Platelets as delivery agents

ABSTRACT

In some embodiments provided herein is a method of preparing cargo-loaded platelets, comprising: treating platelets with a cargo and with a loading buffer comprising a salt, a base, a loading agent, and optionally ethanol, to form the cargo-loaded platelets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/828,041, filed on Apr. 2, 2019, U.S. Provisional Patent Application No. 62/775,141, filed on Dec. 4, 2018, and U.S. Provisional Patent Application No. 62/773,931, filed on Nov. 30, 2018. The contents of each of these applications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure in some embodiments relates to the use of platelets, platelet derivatives, or thrombosomes (e.g., freeze-dried platelet derivatives) as biological carriers of cargo, such as pharmaceutical drugs, also referred to herein as drug-loaded platelets, platelet derivatives, or thrombosomes. Also provided herein in some embodiments are methods of preparing platelets, platelet derivatives, or thrombosomes loaded with the drug of interest.

The present disclosure relates to the field of blood and blood products. More specifically, it relates to platelets, cryopreserved platelets, and/or lyopreserved platelet compositions, including those containing stabilized platelets or compositions derived from platelets. The drug-loaded platelets can be stored under typical ambient conditions, refrigerated, cryopreserved, for example with dimethyl sulfoxide (DMSO), and/or lyophilized after stabilization (e.g., thrombosomes)

BACKGROUND

Blood is a complex mixture of numerous components. In general, blood can be described as comprising four main parts: red blood cells, white blood cells, platelets, and plasma. The first three are cellular or cell-like components, whereas the fourth (plasma) is a liquid component comprising a wide and variable mixture of salts, proteins, and other factors necessary for numerous bodily functions. The components of blood can be separated from each other by various methods. In general, differential centrifugation is most commonly used currently to separate the different components of blood based on size and, in some applications, density.

Unactivated platelets, which are also commonly referred to as thrombocytes, are small, often irregularly-shaped (e.g., discoidal or ovoidal) megakaryocyte-derived components of blood that are involved in the clotting process. They aid in protecting the body from excessive blood loss due not only to trauma or injury, but to normal physiological activity as well. Platelets are considered crucial in normal hemostasis, providing the first line of defense against blood escaping from injured blood vessels. Platelets generally function by adhering to the lining of broken blood vessels, in the process becoming activated, changing to an amorphous shape, and interacting with components of the clotting system that are present in plasma or are released by the platelets themselves or other components of the blood. Purified platelets have found use in treating subjects with low platelet count (thrombocytopenia) and abnormal platelet function (thrombasthenia). Concentrated platelets are often used to control bleeding after injury or during acquired platelet function defects or deficiencies, for example those occurring during surgery and those due to the presence of platelet inhibitors.

Loading platelets with pharmaceutical drugs may allow targeted delivery of the drugs to sites of interest. Further, drug-loaded platelets may be lyophilized or cryopreserved to allow for long-term storage. In some embodiments the loading of a drug in the platelets mitigates systemic side effects associated with the drug and lowers the threshold of therapeutic dose necessary by facilitating targeted treatment at site of interest. See, Xu. P., et. al., Doxorubicin-loaded platelets as a smart drug delivery system: An improved therapy for lymphoma, Scientific Reports, 7, Article Number: 42632, (2017).

SUMMARY OF THE INVENTION

In some embodiments provided herein is a method of preparing cargo-loaded platelets, cargo-loaded platelet derivatives, or cargo-loaded thrombosomes (e.g., freeze-dried platelet derivatives), comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         cargo and with at least one loading agent and optionally one or         more plasticizers such as organic solvents, such as organic         solvents selected from the group consisting of ethanol, acetic         acid, acetone, acetonitrile, dimethylformamide, dimethyl         sulfoxide, dioxane, methanol, n-propanol, isopropanol,         tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide         (DMAC), or combinations thereof,     -   to form the cargo-loaded platelets, cargo-loaded platelet         derivatives, or cargo-loaded thrombosomes.

In some embodiments, the method of preparing cargo-loaded platelets can include treating the platelets, the platelet derivatives, and/or the thrombosomes with the cargo with one loading agent. In some embodiments, the method of preparing cargo-loaded platelets, cargo-loaded platelet derivatives, or cargo-loaded thrombosomes can include treating the platelets, the platelet derivatives, or the thrombosomes with the cargo with multiple loading agents.

In some embodiments, suitable organic solvents include, but are not limited to alcohols, esters, ketones, ethers, halogenated solvents, hydrocarbons, nitriles, glycols, alkyl nitrates, water or mixtures thereof. In some embodiments, suitable organic solvents includes, but are not limited to methanol, ethanol, n-propanol, isopropanol, acetic acid, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, isopropyl acetate, tetrahydrofuran, isopropyl ether (IPE), tert-butyl methyl ether, dioxane (e.g., 1,4-dioxane), acetonitrile, propionitrile, methylene chloride, chloroform, toluene, anisole, cyclohexane, hexane, heptane, ethylene glycol, nitromethane, dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone, dimethylacetamide, and combinations thereof. The presence of organic solvents, such as ethanol, can be beneficial in the processing of platelets, platelet derivatives, and/or thrombosomes. In particular, the organic solvent may open up and/or increase the flexibility of the plasma membrane of the platelets, platelet derivatives, and/or thrombosomes, which allows a higher amount of cargo (e.g., drug) to be loaded into the platelets, platelet derivatives, and/or thrombosomes. In some embodiments, the organic solvent can aid in solubilizing molecules to be loaded.

In some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         drug and with a loading buffer comprising a base, a loading         agent, and optionally at least one organic solvent such as an         organic solvent selected from the group consisting of ethanol,         acetic acid, acetone, acetonitrile, dimethylformamide, dimethyl         sulfoxide, dioxane, methanol, n-propanol, isopropanol,         tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide         (DMAC), or combinations thereof,     -   to form the drug-loaded platelets, the drug-loaded platelet         derivatives, or the drug-loaded thrombosomes.

In some embodiments provided herein is a method of preparing cargo-loaded platelets, cargo-loaded platelet derivatives, or cargo-loaded thrombosomes, comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         cargo and with a loading buffer comprising a salt, a base, a         loading agent, and optionally at least one organic solvent     -   to form the cargo-loaded platelets, cargo-loaded platelet         derivatives, or the cargo-loaded thrombosomes.

In some embodiments provided herein is a method of preparing cargo-loaded platelets, cargo-loaded platelet derivatives, or cargo-loaded thrombosomes, comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         cargo and with a loading agent and optionally at least one         organic solvent     -   to form the cargo-loaded platelets, the cargo-loaded platelet         derivatives, or the cargo-loaded thrombosomes.

In some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         drug and with a loading buffer comprising a base, a loading         agent, and optionally at least one organic solvent     -   to form the drug-loaded platelets, the drug-loaded platelet         derivatives, or the drug-loaded thrombosomes.

In some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   treating platelets, platelet derivatives, or thrombosomes with a         drug and with a loading buffer comprising a salt, a base, a         loading agent, and optionally at least one organic solvent     -   to form the drug-loaded platelets, the drug-loaded platelet         derivatives, or the drug-loaded thrombosomes.

In some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   a) providing platelets, platelet derivatives, or thrombosomes;         -   and     -   b) treating the platelets, the platelet derivatives, or the         thrombosomes with a drug and with a loading buffer comprising a         salt, a base, a loading agent, and optionally at least one         organic solvent         -   to form the drug-loaded platelets, drug-loaded platelet             derivatives, or the drug-loaded thrombosomes.

In some embodiments, the method further comprises cryopreserving the drug-loaded platelets, drug-loaded platelet derivatives, or the drug-loaded thrombosomes. In some embodiments, the method further comprises cold storing the drug-loaded platelets, drug-loaded platelet derivatives, or the drug-loaded thrombosomes. In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives. In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising at least 10% of the amount of the drug of step (b).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising from about 1 nM to about 100 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug.

In some embodiments, the platelets, platelet derivatives, or thrombosomes are treated with the drug and with the buffer sequentially, in either order.

Thus, in some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   (1) treating platelets, platelet derivatives, or thrombosomes         with a drug to form a first composition; and     -   (2) treating the first composition with a buffer comprising a         salt, a base, a loading agent, and optionally at least one         organic solvent to form the drug-loaded platelets, drug-loaded         platelet derivatives, or drug-loaded thrombosomes.

In some embodiments of the methods of preparing cargo-loaded platelets, such as drug-loaded platelets, as provided herein, the methods do not comprise treating platelets, platelet derivatives, or thrombosomes with ethanol.

In some embodiments of the methods of preparing cargo-loaded platelets, such as drug-loaded platelets, as provided herein, the methods do not comprise treating platelets, platelet derivatives, or thrombosomes with a solvent selected from the group consisting of ethanol, acetic acid, acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, dioxane, methanol, n-propanol, isopropanol, tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide (DMAC), or combinations thereof.

In some embodiments of the methods of preparing cargo-loaded platelets, such as drug-loaded platelets, as provided herein, the methods do not comprise treating platelets, platelet derivatives, or thrombosomes with an organic solvent.

In some embodiments of the methods of preparing cargo-loaded platelets, such as drug-loaded platelets, as provided herein, the methods do not comprise treating platelets, platelet derivatives, or thrombosomes with a solvent.

In some embodiments of the methods of preparing cargo-loaded platelets, such as drug-loaded platelets, as provided herein, the methods comprise treating platelets, platelet derivatives, or thrombosomes with a solvent, such as an organic solvent, such as organic solvent selected from the group consisting of ethanol, acetic acid, acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, dioxane, methanol, n-propanol, isopropanol, tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide (DMAC), or combinations thereof, such as ethanol.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives obtained in step (2). In some embodiments, the method further comprises cryopreserving, lyopreserving (e.g., freeze-drying) the drug-loaded platelets or the drug-loaded platelet derivatives. In some embodiments, the method further comprises cold storing the drug-loaded platelets, the drug-loaded platelet derivatives, the drug-loaded thrombosomes, or compositions containing drug-loaded platelets at suitable storage temperatures, such as standard room temperature storing (e.g., storing at a temperature ranging from about 20 to about 30° C.) or cold storing (e.g., storing at a temperature ranging from about 1 to about 10° C.). In some embodiments, the method further comprises cryopreserving, freeze-drying, thawing, rehydrating, and combinations thereof, the drug loaded platelets, the drug-loaded platelet derivatives, or the drug-loaded thrombosomes. For example, in such embodiments, the method may further comprise rehydrating the drug-loaded platelets, the drug-loaded platelet derivatives, or the drug-loaded thrombosomes obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising at least 10% of the amount of the drug of step (1).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 100 mM, such as about 100 nM to 10 mM, of the drug of step (1).

In some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   (1) treating the platelets, platelet derivatives, or         thrombosomes with a buffer comprising a salt, a base, a loading         agent, and optionally ethanol, to form a first composition; and     -   (2) treating the first composition with a drug, to form the         drug-loaded platelets, the drug-loaded platelet derivatives, or         the drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets, the drug-loaded platelet derivatives, or the drug-loaded thrombosomes obtained in step (2). In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising at least 10% of the amount of the drug of step (2).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug of step (2).

In some embodiments, the platelets or thrombosomes are treated with the drug and with the buffer concurrently.

Thus, in some embodiments provided herein is a method of preparing drug-loaded platelets, the drug-loaded platelet derivatives, or the drug-loaded thrombosomes, comprising:

-   -   treating the platelets, the platelet derivatives, or the         thrombosomes with a drug in the presence of a buffer comprising         a salt, a base, a loading agent, and optionally ethanol, to form         the drug-loaded platelets, the drug-loaded platelet derivatives,         or the drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives. In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or the thrombosomes comprising at least 10% of the amount of the drug prior to loading.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug.

In some embodiments, platelets, platelet derivatives, or thrombosomes are pooled from a plurality of donors. Such platelets, platelet derivatives, and thrombosomes pooled from a plurality of donors may be also referred herein to as pooled platelets, platelet derivatives, or thrombosomes. In some embodiments, the donors are more than 5, such as more than 10, such as more than 20, such as more than 50, such as up to about 100 donors. In some embodiments, the donors are from about 5 to about 100, such as from about 10 to about 50, such as from about 20 to about 40, such as from about 25 to about 35.

Thus, provided herein in some embodiments is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes comprising

-   -   A) pooling platelets, platelet derivatives, or thrombosomes from         a plurality of donors; and     -   B) treating the platelets, platelet derivatives, or thrombosomes         from step (A) with a drug and with a loading buffer comprising a         salt, a base, a loading agent, and optionally ethanol, to form         the drug-loaded platelets, the drug-loaded platelet derivatives,         or the drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives obtained in step (B). In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or rehydrated platelet derivatives comprising at least 10% of the amount of the drug of step (B).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or rehydrated platelet derivatives comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug of step (B).

In some embodiments, the pooled platelets, platelet derivatives, or thrombosomes are treated with the drug and with the buffer sequentially, in either order.

Thus, provided herein in some embodiments is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes comprising:

-   -   A) pooling platelets, platelet derivatives, or thrombosomes from         a plurality of donors; and     -   B)         -   (1) treating the platelets, platelet derivatives, or             thrombosomes from step (A) with a drug to form a first             composition; and         -   (2) treating the first composition with a buffer comprising             a salt, a base, a loading agent, and optionally ethanol, to             form the drug-loaded platelets, drug-loaded platelet             derivatives, or drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives obtained in step (B)(2). In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or rehydrated platelet derivatives comprising at least 10% of the amount of the drug of step (B)(1).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or platelet derivatives comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug of step (B)(1).

Thus, provided herein in some embodiments is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes comprising:

-   -   A) pooling platelets, platelet derivatives, or thrombosomes from         a plurality of donors; and     -   B)         -   (1) treating the platelets, the platelet derivatives, or the             thrombosomes from step (A) with a buffer comprising a salt,             a base, a loading agent, and optionally ethanol, to form a             first composition; and         -   (2) treating the first composition with a drug to form the             drug-loaded platelets, the drug-loaded platelet derivatives,             or the drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives obtained in step (B)(2). In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising at least 10% of the amount of the drug of step (B)(2).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug of step (B)(2).

In some embodiments, the pooled platelets, platelet derivatives, or thrombosomes are treated with the drug and with the buffer concurrently.

Thus, in some embodiments provided herein is a method of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes, comprising:

-   -   A) pooling platelets, platelet derivatives, or thrombosomes from         a plurality of donors; and     -   B) treating the platelets, the platelet derivatives, or the         thrombosomes with a drug in the presence of a buffer comprising         a salt, a base, a loading agent, and optionally ethanol, to form         the drug-loaded platelets, the drug-loaded platelet derivatives,         or the drug-loaded thrombosomes.

In some embodiments, the method further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives obtained in step (B). In some embodiments, the method further comprises freeze-drying the drug-loaded platelets or the drug-loaded platelet derivatives. In such embodiments, the method may further comprise rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step.

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising at least 10% of the amount of the drug of step (B).

In some embodiments, the method that further comprises drying the drug-loaded platelets or the drug-loaded platelet derivatives and rehydrating the drug-loaded platelets or the drug-loaded platelet derivatives obtained from the drying step provides rehydrated platelets or thrombosomes comprising from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, of the drug of step (B).

In some embodiments, the methods of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes that comprise pooling platelets, platelet derivatives, or thrombosomes from a plurality of donors comprise a viral inactivation step.

In some embodiments, the methods of preparing drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes that comprise pooling platelets, platelet derivatives, or thrombosomes from a plurality of donors do not comprise a viral inactivation step.

In some embodiments, the platelets, the platelet derivatives, or the thrombosomes are loaded with the drug in a period of time of 5 minutes to 48 hours, such as 10 minutes to 24 hours, such as 20 minutes to 12 hours, such as 30 minutes to 6 hours, such as 1 hour minutes to 3 hours, such as about 2 hours. In some embodiments, a concentration of drug from about 1 nM to about 1000 mM, such as about 10 nM to about 10 mM, such as about 100 nM to 1 mM, is loaded in a period of time of 5 minutes to 48 hours, such as 10 minutes to 24 hours, such as 20 minutes to 12 hours, such as 30 minutes to 6 hours, such as 1 hour minutes to 3 hours, such as about 2 hours.

In some embodiments provided herein are drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes prepared by a method as disclosed herein. In some embodiments provided herein are rehydrated platelets, platelet derivatives, or thrombosomes prepared by a method as disclosed herein.

In some embodiments provided herein are drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes prepared with Prostaglandin E1 (PGE1) or Prostacyclin. In some embodiments provided herein are drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes that are not prepared with Prostaglandin E1 (PGE1) or Prostacyclin.

In some embodiments provided herein are drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes prepared with a chelating agent such as EGTA. In some embodiments provided herein are drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes that are not prepared with a chelating agent such as EGTA.

In some embodiments provided herein the method includes treating the first composition with Prostaglandin 1 (PGE1) or Prostacyclin. In some embodiments provided herein the method does not include treating the first composition with Prostaglandin 1 (PGE1) or Prostacyclin.

In some embodiments provided herein the method includes treating the first composition with a chelating agent such as EGTA. In some embodiments provided herein the method does not include treating the first composition with a chelating agent such as EGTA.

Drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes may shield the drug from exposure in circulation, thereby reducing or eliminating systemic toxicity (e.g. cardiotoxicity) associated with the drug. Drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes may also protect the drug from metabolic degradation or inactivation.

Accordingly, in some embodiments, provided herein is a method of treating a disease as disclosed herein, comprising administering drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes as disclosed herein. Accordingly, in some embodiments, provided herein is a method of treating a disease as disclosed herein, comprising administering cold stored, room temperature stored, cryopreserved thawed, rehydrated, and/or lyophilized platelets, platelet derivatives, or thrombosomes as disclosed herein. In some embodiments, the disease is, Traumatic Brain injury. In some embodiments, the disease is, ITP. In some embodiments, the disease is TTP.

DESCRIPTION OF DRAWINGS

FIG. 1 shows saponin-mediated permeabilization of platelets measured using standard light transmission aggregometry (LTA).

FIG. 2 provides median fluorescence measured using flow cytometry of platelets incubated in the presence of saponin to show the effect of saponin on the permeabilization of platelet cell membranes.

FIG. 3 shows flow cytometry data providing endocytotic loading efficiency of BODIPY-vancomycin, FITC-bovine IgG, Fab2, and FITC-albumin in platelets.

FIG. 4 shows flow cytometry data providing endocytotic loading efficiency of fluorescently-labeled BODIPY-vancomycin was loaded into platelets via fluid phase endocytosis over different incubation time periods.

FIG. 5 shows fluorescent intensity for samples prepared with different hypertonic pre-treatment solutions containing variable amounts of dextrose.

FIG. 6 shows cell counts (gated by size) for samples prepared with differing hypertonic pre-treatment solutions containing variable amounts of dextrose.

FIG. 7 shows cell size for samples prepared with differing hypertonic pre-treatment solutions containing variable amounts of dextrose.

FIG. 8 shows platelet aggregation in response to collagen for samples prepared with differing hypertonic pre-treatment solutions containing variable amounts of dextrose.

FIG. 9 is a histogram of platelet+/−Phalloidin-CF488A FITC-H intensity on a bio-exponential scale.

FIG. 10 shows mean platelet FITC-H intensity by flow cytometry for samples with or without 5 U/mL Phalloidin-CF488A and with or without electroporation.

FIG. 11 is a histogram of platelet+/−Streptavidin-Dylight 488 FITC-H intensity on a bio-exponential scale.

FIG. 12 shows mean platelet FITC-H intensity by flow cytometry for samples with or without 150 μg/mL Streptavidin-Dylight 488 and with or without electroporation.

FIG. 13 is a histogram of Lucifer yellow fluorescence in platelets under various loading conditions.

FIG. 14 shows Lucifer yellow fluorescence in platelets under various loading conditions.

DETAILED DESCRIPTION

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the term belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The present disclosure is controlling to the extent it conflicts with any incorporated publication.

As used herein and in the appended claims, the term “platelet” can include whole platelets, fragmented platelets, platelet derivatives, or thrombosomes. Thus, for example, reference to “drug-loaded platelets” may be inclusive of drug-loaded platelets as well as drug-loaded platelet derivatives or drug-loaded thrombosomes, unless the context clearly dictates a particular form.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a platelet” includes a plurality of such platelets. Furthermore, the use of terms that can be described using equivalent terms include the use of those equivalent terms. Thus, for example, the use of the term “subject” is to be understood to include the terms “patient”, “individual” and other terms used in the art to indicate one who is subject to a treatment.

In some embodiments, rehydrating the drug-loaded platelets comprises adding to the platelets an aqueous liquid. In some embodiments, the aqueous liquid is water. In some embodiments, the aqueous liquid is an aqueous solution. In some embodiments, the aqueous liquid is a saline solution. In some embodiments, the aqueous liquid is a suspension.

In some embodiments, the rehydrated platelets have coagulation factor levels showing all individual factors (e.g., Factors VII, VIII and IX) associated with blood clotting at 40 international units (IU) or greater.

In some embodiments, the dried platelets, such as freeze-dried platelets, have less than about 10%, such as less than about 8%, such as less than about 6%, such as less than about 4%, such as less than about 2%, such as less than about 0.5% crosslinking of platelet membranes via proteins and/or lipids present on the membranes. In some embodiments, the rehydrated platelets, have less than about 10%, such as less than about 8%, such as less than about 6%, such as less than about 4%, such as less than about 2%, such as less than about 0.5% crosslinking of platelet membranes via proteins and/or lipids present on the membranes.

In some embodiments, the drug-loaded platelets and the dried platelets, such as freeze-dried platelets, having a particle size (e.g., diameter, max dimension) of at least about 0.2 μm (e.g., at least about 0.3 μm, at least about 0.4 μm, at least about 0.5 μm, at least about 0.6 μm, at least about 0.7 μm, at least about 0.8 μm, at least about 0.9 μm, at least about 1.0 μm, at least about 1.0 μm, at least about 1.5 μm, at least about 2.0 μm, at least about 2.5 μm, or at least about 5.0 μm). In some embodiments, the particle size is less than about 5.0 μm (e.g., less than about 2.5 μm, less than about 2.0 μm, less than about 1.5 μm, less than about 1.0 μm, less than about 0.9 μm, less than about 0.8 μm, less than about 0.7 μm, less than about 0.6 μm, less than about 0.5 μm, less than about 0.4 μm, or less than about 0.3 μm). In some embodiments, the particle size is from about 0.3 μm to about 5.0 μm (e.g., from about 0.4 μm to about 4.0 μm, from about 0.5 μm to about 2.5 μm, from about 0.6 μm to about 2.0 μm, from about 0.7 μm to about 1.0 μm, from about 0.5 μm to about 0.9 μm, or from about 0.6 μm to about 0.8 μm).

In some embodiments, at least 50% (e.g., at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99%) of platelets and/or the dried platelets, such as freeze-dried platelets, have a particle size in the range of about 0.3 μm to about 5.0 μm (e.g., from about 0.4 μm to about 4.0 μm, from about 0.5 μm to about 2.5 μm, from about 0.6 m to about 2.0 μm, from about 0.7 μm to about 1.0 μm, from about 0.5 μm to about 0.9 μm, or from about 0.6 μm to about 0.8 μm). In some embodiments, at most 99% (e.g., at most about 95%, at most about 80%, at most about 75%, at most about 70%, at most about 65%, at most about 60%, at most about 55%, or at most about 50%) of platelets and/or the dried platelets, such as freeze-dried platelets, are in the range of about 0.3 μm to about 5.0 μm (e.g., from about 0.4 m to about 4.0 μm, from about 0.5 μm to about 2.5 μm, from about 0.6 μm to about 2.0 μm, from about 0.7 μm to about 1.0 μm, from about 0.5 μm to about 0.9 μm, or from about 0.6 μm to about 0.8 μm). In some embodiments, about 50% to about 99% (e.g., about 55% to about 95%, about 60% to about 90%, about 65% to about 85, about 70% to about 80%) of platelets and/or the dried platelets, such as freeze-dried platelets, are in the range of about 0.3 μm to about 5.0 m (e.g., from about 0.4 μm to about 4.0 μm, from about 0.5 μm to about 2.5 μm, from about 0.6 μm to about 2.0 μm, from about 0.7 μm to about 1.0 μm, from about 0.5 μm to about 0.9 μm, or from about 0.6 μm to about 0.8 μm).

In some embodiments, platelets are isolated prior to treating the platelets with a drug.

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) isolating platelets, for example in a liquid medium;         -   and     -   b) treating the platelets with a drug and with a loading buffer         comprising a salt, a base, a loading agent, and optionally         ethanol, to form the drug-loaded platelets,

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) isolating platelets, for example in a liquid medium;     -   b) treating the platelets with a drug to form a first         composition; and     -   c) treating the first composition with a buffer comprising a         salt, a base, a loading agent, and optionally at least one         organic solvent to form the drug-loaded platelets.

In some embodiments, suitable organic solvents include, but are not limited to alcohols, esters, ketones, ethers, halogenated solvents, hydrocarbons, nitriles, glycols, alkyl nitrates, water or mixtures thereof. In some embodiments, suitable organic solvents includes, but are not limited to methanol, ethanol, n-propanol, isopropanol, acetic acid, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, isopropyl acetate, tetrahydrofuran, isopropyl ether (IPE), tert-butyl methyl ether, dioxane (e.g., 1,4-dioxane), acetonitrile, propionitrile, methylene chloride, chloroform, toluene, anisole, cyclohexane, hexane, heptane, ethylene glycol, nitromethane, dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone, dimethylacetamide, and combinations thereof.

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) isolating platelets, for example in a liquid medium;     -   b) treating the platelets with a buffer comprising a salt, a         base, a loading agent, and optionally at least one organic         solvent, to form a first composition; and     -   c) treating the first composition with a drug, to form the         drug-loaded platelets.

In some embodiments, no solvent is used. Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   c) isolating platelets, for example in a liquid medium;         -   and     -   d) treating the platelets with a drug and with a loading buffer         comprising a salt, a base, and a loading agent, to form the         drug-loaded platelets,         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol.

Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   d) isolating platelets, for example in a liquid medium;     -   e) treating the platelets with a drug to form a first         composition; and     -   f) treating the first composition with a buffer comprising a         salt, a base, and a loading agent, to form the drug-loaded         platelets,         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol and the method does             not comprise treating the first composition with an organic             solvent such as ethanol.

Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) isolating platelets, for example in a liquid medium;     -   b) treating the platelets with a buffer comprising a salt, a         base, and a loading agent, to form a first composition; and     -   c) treating the first composition with a drug, to form the         drug-loaded platelets.         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol and the method does             not comprise treating the first composition with an organic             solvent such as ethanol.

In some embodiments, isolating platelets comprises isolating platelets from blood.

In some embodiments, platelets are donor-derived platelets. In some embodiments, platelets are obtained by a process that comprises an apheresis step.

In some embodiments, platelets are derived in vitro. In some embodiments, platelets are derived or prepared in a culture prior to treating the platelets with a drug. In some embodiments, preparing the platelets comprises deriving or growing the platelets from a culture of megakaryocytes. In some embodiments, preparing the platelets comprises deriving or growing the platelets (or megakaryocytes) from a culture of human pluripotent stem cells (PCSs), including embryonic stem cells (ESCs) and/or induced pluripotent stem cells (iPSCs).

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) preparing platelets;         -   and     -   b) treating the platelets with a drug and with a loading buffer         comprising a salt, a base, a loading agent, and optionally at         least one organic solvent, to form the drug-loaded platelets.

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) preparing platelets;     -   b) treating the platelets with a drug to form a first         composition; and     -   c) treating the first composition with a buffer comprising a         salt, a base, a loading agent, and optionally at least one         organic solvent, to form the drug-loaded platelets.

Accordingly, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) preparing platelets;     -   b) treating the platelets with a buffer comprising a salt, a         base, a loading agent, and optionally at least one organic         solvent, to form a first composition; and     -   c) treating the first composition with a drug, to form the         drug-loaded platelets.

In some embodiments, no solvent is used. Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) preparing platelets;         -   and     -   b) treating the platelets with a drug and with a loading buffer         comprising a salt, a base, and a loading agent, to form the         drug-loaded platelets,         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol.

Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   a) preparing platelets;     -   b) treating the platelets with a drug to form a first         composition; and     -   c) treating the first composition with a buffer comprising a         salt, a base, and a loading agent, to form the drug-loaded         platelets,         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol and the method does             not comprise treating the first composition with an organic             solvent such as ethanol.

Thus, in some embodiments, the method for preparing drug-loaded platelets comprises:

-   -   d) preparing platelets;     -   e) treating the platelets with a buffer comprising a salt, a         base, and a loading agent, to form a first composition; and     -   f) treating the first composition with a drug, to form the         drug-loaded platelets.         -   wherein the method does not comprise treating the platelets             with an organic solvent such as ethanol and the method does             not comprise treating the first composition with an organic             solvent such as ethanol.

In some embodiments, the loading agent is a saccharide. In some embodiments, the saccharide is a monosaccharide. In some embodiments, the saccharide is a disaccharide. In some embodiments, the saccharide is a non-reducing disaccharide. In some embodiments, the saccharide is sucrose, maltose, trehalose, glucose (e.g., dextrose), mannose, or xylose. In some embodiments, the loading agent is a starch.

In some embodiments, the loading agent is a detergent. In some embodiments, the detergent is saponin. In some embodiments, the loading agent (e.g., detergent, saponin) can be present in a composition (e.g., buffer) in an amount of about 1 microgram, about 5 micrograms, about 10 micrograms, about 20 micrograms, about 30 micrograms, about 40 micrograms, about 50 micrograms, about 60 micrograms, about 70 micrograms, about 80 micrograms, about 90 micrograms, or about 100 micrograms. In some embodiments, the loading agent (e.g., detergent, saponin) can be present in the composition (e.g., buffer) in an amount of at least about 1 microgram, such as at least about 5 micrograms, at least about 10 micrograms, at least about 20 micrograms, at least about 30 micrograms, at least about 40 micrograms, at least about 50 micrograms, at least about 60 micrograms, or at least about 70 micrograms. In some embodiments, the loading agent (e.g., detergent, saponin) can be present in a composition (e.g., buffer) in an amount less than about 100 micrograms, such as less than about 90 micrograms, less than about 80 micrograms, less than about 70 micrograms, less than about 60 micrograms, less than about 50 micrograms, less than about 40 micrograms, less than about 30 micrograms, or less than about 20 micrograms. In some embodiments, the loading agent (e.g., detergent, saponin) can be present in a composition (e.g., buffer) in an amount of from about 1 microgram to about 100 micrograms, such as from about 3 micrograms to about 50 micrograms, from about 5 micrograms to about 25 micrograms, from about 10 micrograms to about 20 micrograms, from about 20 micrograms to about 80 micrograms, from about 30 micrograms to about 70 micrograms, or from about 40 micrograms to about 60 micrograms.

In some embodiments, the loading agent is a carrier protein. In some embodiments, the carrier protein is albumin. In some embodiments, the carrier protein is bovine serum albumin (BSA).

As used herein, the term “drug” refers to any pharmaceutically active ingredient other than a microRNA (also known as miRNA) and/or a small interfering RNA (also known as siRNA, short interfering RNA, or silencing RNA) and/or a messenger RNA (also known as mRNA). Additionally, the term “drug” refers to any pharmaceutically active ingredient other than any drug used in the treatment of cancer.

As used herein, the term “microRNA” refers to a ribonucleic acid duplex that targets and silences an mRNA molecule. Many miRNAs are naturally-occurring, but miRNAs can also be synthesized by those of ordinary skill in the art. Mature miRNAs are generally 19-25 nucleotides in length, have 3′ overhangs of two nucleotides, target multiple mRNAs and are typically only partially complementary to their target mRNAs. miRNAs typically function by repressing translation and facilitating mRNA degradation.

As used herein, the term “small interfering RNA” refers to a double-stranded RNA that targets and silences an mRNA molecule. Many siRNAs are naturally-occurring, but siRNAs can also be synthesized by those of ordinary skill in the art. siRNA are generally derived from strands of exogenous growing (originating from outside an organism) RNA, which is taken up by the cell and undergoes further processing. Mature siRNAs are generally 19-27nucleotides in length, have 3′ overhangs of two nucleotides at each end that can be used to “interfere” with the translation of proteins by binding to and promoting the degradation of messenger RNA at specific sequences. Each siRNA strand has a 5′ phosphate group and a 3′ hydroxyl (OH) group. siRNA can be produced from dsRNA or hairpin looped RNA and processed into siRNAs by the Dicer enzyme. siRNA can also be incorporated into a multi-subunit protein complex called RNA-induced silencing complex (RISC).

As used herein, the term “mRNA” refers to a single-stranded ribonucleic acid molecule used by cells for the translation of DNA into protein. Many mRNAs are naturally-occurring, but mRNAs can also be synthesized by those of ordinary skill in the art. Mature mRNAs can vary greatly in size and composition. mRNAs are necessary components of protein synthesis after exportation from the nucleus to the cytoplasm of the cell.

miRNAs and siRNAs are distinct from other types of RNA molecules including, without limitation, messenger (“mRNA”), ribosomal RNA (“rRNA”), small nuclear RNA (“snRNA”), transfer RNA (“tRNA”), and short hairpin RNA (“shRNA”). rRNA, snRNA, tRNA, and shRNA are all encompassed within the term “drug” as used herein. mRNA, rRNA, snRNA, and tRNA are canonical classes of RNA molecules, the function and structure of which are well-known to those of ordinary skill in the art.

shRNAs are short linear RNA molecules, portions of which associate with each other via base pairing to form a double stranded stem region (as opposed to the fully double stranded siRNAs), resulting in a characteristic “hairpin” or loop at one end of the molecule. Unlike miRNAs and siRNAs, shRNAs are typically introduced into cells using methods that differ from the methods used for introducing miRNA and siRNA (e.g., using transfection methods). For example, shRNAs can be introduced via plasmids or, alternatively, through viral or bacterial vectors. Both of these methods are DNA-based techniques, where the shRNA is transcribed, processed by the enzyme Drosha, and then further processed into siRNAs, by the Dicer enzyme, to eventually mediate RNAi.

As used herein, “thrombosomes” (sometimes also herein called “Tsomes” or “Ts”, particularly in the Examples and Figures) are platelet derivatives that have been treated with an incubating agent (e.g., any of the incubating agents described herein) and lyopreserved (e.g., freeze-dried). In some cases, thrombosomes can be prepared from pooled platelets. Thrombosomes can have a shelf life of 2-3 years in dry form at ambient temperature and can be rehydrated with sterile water within minutes for immediate infusion.

In some embodiments, the drug is selected from the group consisting of one of the following:

-   -   i. a small molecule (that is, an organic compound having a         molecular weight up to about 2 KDalton);     -   ii. a protein;     -   iii. an oligopeptide;     -   iv. a non-miRNA nucleic acid, a non-siRNA, and/or a non-mRNA         (e.g., non-miRNA, DNA, other naturally or non-naturally         occurring nucleic acids, including various modifications         thereof);         -   and     -   v. an aptamer.

In various methods described herein, platelets are loaded with one or more any of a variety of drugs. In some embodiments, platelets are loaded with a small molecule. For example, platelets can be loaded with one or more of, sirolimus (rapamycin), 2,4 diamino-quinazoline, vitamin D, retinoic acid, aspirin, sulindac (CLINORIL®, Aflodac), 2,4 diamino-quinazoline derivatives, curcumin (e.g., Meriva®), quercetin, epigallocatechin gallate (EGCG), resveratrol, celecoxib (CELEBREX®), tautomycin, niclosamide (NICLOCIDE™), cambinol, filipin, ethacrynic acid, ethacryinic acid derivatives, shikonin, shikonin derivatives (e.g., deoxyshikonin, isobutyrylshikonin, acetylshikonin, β,β-dimethylacrylshikonin acetylalkannin), gentamicin, amikamicin, emodin, all-trans retinoic acid (ATRA), valproic acid, LOU064, VM-902A, EZM8266, LCB03-0110, tofacitinib, oclacitinib, baricitinib (OLUMIANT®; LY-3009104, INCB-28050), filgotinib (G-146034, GLPG-0634), gotinib (LY-2784544), PF-04965842, upadacitinib (ABT-494), peficitinib (ASP015K, JNJ-54781532), and axathioprine.

In various methods described herein, platelets are loaded with one or more any of a variety of drugs. In some embodiments, platelets are loaded with a protein (e.g., an antibody or antibody conjugate). For example, platelets can be loaded with one or more of, abciximab, adalimumab, alefacept, golimumab, certolizumab, omalizumab, reteplase, alteplase, anistreplase, and infliximab.

In various methods described herein, platelets are loaded with one or more any of a variety of drugs. In some embodiments, platelets are loaded with an oligopeptide. For example, platelets can be loaded with one or more of, Histrelin, Gonadorelin, octreotide, Nafarelin, Abarelix, Cetrorelix, Ganirelix, and Somatostatin.

In various methods described herein, platelets are loaded with one or more any of a variety of drugs. In some embodiments, platelets are loaded with a non-miRNA, non-siRNA, or non-mRNA nucleic acid (e.g., non-miRNA, DNA, other naturally or non-naturally occurring nucleic acids, including various modifications thereof). For example, platelets can be loaded with one or more of, miravirsen, ISIS-104838, ISIS-113715, ISIS-301012, ISIS-304801, ISIS-329993, ISIS-404173, ISIS-426115, ISIS-449884, ISIS-463588, ISIS-494372, ISIS-416858, SPC3649, and Tat/Rev shRNA.

In various methods described herein, platelets are loaded with one or more any of a variety of drugs. In some embodiments, platelets are loaded with an aptamer. For example, platelets can be loaded with one or more of ARC 19499 (BAX499), pegaptanib, REG1 (RB006, RB007), E10030, ARC 1905, NOX-E36, NOX-H94, ARC 1779, NU172, CD28-apt2, CD28-apt7 (RNA), and EYE001.

In some embodiments, a drug loaded into platelets is modified. For example, a drug can be modified to increase its stability during the platelet loading process, while the drug is loaded into the platelet, and/or after the drug's release from a platelet. In some embodiments, the modified drug's stability is increased with little or no adverse effect on its activity. For example, the modified drug can have at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more of the activity of the corresponding unmodified drug. In some embodiments, the modified drug has 100% (or more) of the activity of the corresponding unmodified drug. Various modifications that stabilize drugs are known in the art. In some embodiments, the drug is a nucleic acid, which nucleic acid is stabilized by one or more of a stabilizing oligonucleotide (see, e.g., U.S. Application Publication No. 2018/0311176), a backbone/side chain modification (e.g., a 2-sugar modification such as a 2′-fluor, methoxy, or amine substitution, or a 2′-thio (—SH), 2′-azido (—N3), or 2′-hydroxymethyl (—CH2OH) modification), an unnatural nucleic acid substitution (e.g., an S-glycerol, cyclohexenyl, and/or threose nucleic acid substitution, an L-nucleic acid substitution, a locked nucleic acid (LNA) modification (e.g., the ribose moiety of an LNA nucleotide is modified with an extra bridge connecting the 2′ oxygen and 4′ carbon), conjugation with PEG, a nucleic acid bond modification or replacement (e.g., a phosphorothioate bond, a methylphosphonate bond, or a phosphorodiamidate bond), a reagent or reagents (e.g., intercalating agents such as coralyne, neomycin, and ellipticine; also see US Publication Application Nos. 2018/0312903 and 2017/0198335, each of which are incorporated herein by reference in their entireties, for further examples of stabilizing reagents). In some embodiments, the drug is a polypeptide, which polypeptide is stabilized by one or more of cyclization of the peptide sequence [e.g., between side chains or ends of the peptide sequence (for example, head to tail, N-backbone to N-backbone, end to N-backbone, end to side chain, side chain to N-backbone, side chain to side chain) through disulfide, lanthionine, dicarba, hydrazine, or lactam bridges], a backbone/side chain modification, an unnatural residue substitution (e.g., a D-amino acid, an N-methyl-α-amino acid, a non-proteogenic constrained amino acid or a (3-amino acid), a peptide bond modification or replacement [e.g., NH-amide alkylation, the carbonyl function of the peptide bond can be replaced by CH2 (reduced bond: —CH2-NH—), C(═S) (endothiopeptide, —C(═S)—NH—) or PO2H (phosphonamide, —P(═O)OH—NH—), the NH-amide bond can be exchanged by O (depsipeptide, —CO—O—), S (thioester, —CO—S—) or CH2 (ketomethylene, —CO—CH2-), a retro-inverso bond (—NH—CO—), a methylene-oxy bond (—CH2-), a thiomethylene bond (—CH2-S—), a carba bond (—CH2-CH2-), and a hydroxyethylene bond (—CHOH—CH2-)], a disulfide-bridged conjugation with synthetic aromatics (see e.g., Chen et al. Org Biomol Chem. 2017, 15(8):1921-1929, which is incorporated by reference herein in its entirety), blocking N- or C-terminal ends of the peptide (e.g., by N-acylation, N-pyroglutamate, or C-amidation or the addition of carbohydrate chains through, for example, glycosylation with glucose, xylose, hexose), an N-terminal esterification (phosphoester), a pegylation modification, and a reagent or reagents (see, e.g., US Publication Application No. 2017/0198335). See. e.g., Vlieghe et al. Drug Discovery Today, 2010, 15, 40-56, which is incorporated by reference herein in its entirety.

In some embodiments, a drug loaded into platelets is modified to include an imaging agent. For example, a drug can be modified with an imaging agent in order to image the drug loaded platelet in vivo. In some embodiments, a drug can be modified with two or more imaging agents (e.g., any two or more of the imaging agents described herein). In some embodiments, a drug loaded into platelets is modified with a radioactive metal ion, a paramagnetic metal ion, a gamma-emitting radioactive halogen, a positron-emitting radioactive non-metal, a hyperpolarized NMR-active nucleus, a reporter suitable for in vivo optical imaging, or a beta-emitter suitable for intravascular detection. For example, a radioactive metal ion can include, but is not limited to, positron emitters such as ⁵⁴Cu, ⁴⁸V, ⁵²Fe, ⁵⁵Co, ⁹⁴Tc or ⁶⁸Ga; or gamma-emitters such as ¹⁷¹Tc, ¹¹¹In, ¹¹³In, or ⁶⁷Ga. For example, a paramagnetic metal ion can include, but is not limited to Gd(III), a Mn(II), a Cu(II), a Cr(III), a Fe(III), a Co(II), a Er(II), a Ni(II), a Eu(III) or a Dy(III), an element comprising an Fe element, a neodymium iron oxide (NdFeO3) or a dysprosium iron oxide (DyFeO3). For example, a paramagnetic metal ion can be chelated to a polypeptide or a monocrystalline nanoparticle. For example, a gamma-emitting radioactive halogen can include, but is not limited to ¹²³I, ¹³¹I or ⁷⁷Br. For example, a positron-emitting radioactive non-metal can include, but is not limited to ¹¹C, ¹³N, ¹⁵O, ¹⁷F, ¹⁸F, ⁷⁵Br, ⁷⁶Br or ¹²⁴I. For example, a hyperpolarized NMR-active nucleus can include, but is not limited to ¹³C, ¹⁵N, ¹⁹F, ²⁹Si and ³¹P. For example, a reporter suitable for in vivo optical imaging can include, but is not limited to any moiety capable of detection either directly or indirectly in an optical imaging procedure. For example, the reporter suitable for in vivo optical imaging can be a light scatterer (e.g., a colored or uncolored particle), a light absorber or a light emitter. For example, the reporter can be any reporter that interacts with light in the electromagnetic spectrum with wavelengths from the ultraviolet to the near infrared. For example, organic chromophoric and fluorophoric reporters include groups having an extensive delocalized electron system, e.g. cyanines, merocyanines, indocyanines, phthalocyanines, naphthalocyanines, triphenylmethines, porphyrins, pyrilium dyes, thiapyrilium dyes, squarylium dyes, croconium dyes, azulenium dyes, indoanilines, benzophenoxazinium dyes, benzothiaphenothiazinium dyes, anthraquinones, napthoquinones, indathrenes, phthaloylacridones, trisphenoquinones, azo dyes, intramolecular and intermolecular charge-transfer dyes and dye complexes, tropones, tetrazines, b/s(dithiolene) complexes, bts(benzene-dithiolate) complexes, iodoaniline dyes, b/stS.O-dithiolene) complexes. For example, the reporter can be, but is not limited to a fluorescent, a bioluminescent, or chemiluminescent polypeptide. For example, a fluorescent or chemiluminescent polypeptide is a green florescent protein (GFP), a modified GFP to have different absorption/emission properties, a luciferase, an aequorin, an obelin, a mnemiopsin, a berovin, or a phenanthridinium ester. For example, a reporter can be, but is not limited to rare earth metals (e.g., europium, samarium, terbium, or dysprosium), or fluorescent nanocrystals (e.g., quantum dots). For example, a reporter may be a chromophore that can include, but is not limited to fluorescein, sulforhodamine 101 (Texas Red), rhodamine B, rhodamine 6G, rhodamine 19, indocyanine green, Cy2, Cy3, Cy3.5, Cy5, Cy5.5, Cy7, Marina Blue, Pacific Blue, Oregon Green 88, Oregon Green 514, tetramethylrhodamine, and Alexa Fluor 350, Alexa Fluor 430, Alexa Fluor 532, Alexa Fluor 546, Alexa Fluor 555, Alexa Fluor 568, Alexa Fluor 594, Alexa Fluor 633, Alexa Fluor 647, Alexa Fluor 660, Alexa Fluor 680, Alexa Fluor 700, and Alexa Fluor 750. For example, a beta-emitter can include, but is not limited to radio metals ⁶⁷Cu, ⁸⁹Sr, ⁹⁰Y, ¹⁵³Sm, ¹⁸⁵Re, ¹⁸⁸Re or ¹⁹²Ir, and non-metals ³²P, ³³P, ³⁸S, ³⁸Cl, ³⁹Cl, ⁸²Br and ⁸³Br. In some embodiments, a drug loaded into platelets can be associated with gold or other equivalent metal particles (such as nanoparticles). For example, a metal particle system can include, but is not limited to gold nanoparticles (e.g., Nanogold™).

In some embodiments, a drug loaded into platelets that is modified with an imaging agent is imaged using an imaging unit. The imaging unit can be configured to image the drug loaded platelets in vivo based on an expected property (e.g., optical property from the imaging agent) to be characterized. For example, imaging techniques (in vivo imaging using an imaging unit) that can be used, but are not limited to are: computer assisted tomography (CAT), magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), or bioluminescence imaging (BLI). Chen Z., et. al., Advance of Molecular Imaging Technology and Targeted Imaging Agent in Imaging and Therapy, Biomed Res Int., February 13, doi: 10.1155/2014/819324 (2014) have described various imaging techniques and which is incorporated by reference herein in its entirety.

In some embodiments, such as embodiments wherein the platelets are treated with the drug and the buffer sequentially as disclosed herein, the drug may be loaded in a liquid medium that may be modified to change the proportion of media components or to exchange components for similar products, or to add components necessary for a given application.

In some embodiments the loading buffer, and/or the liquid medium, may comprise one or more of a) water or a saline solution, b) one or more additional salts, or c) a base. In some embodiments, the loading buffer, and/or the liquid medium, may comprise one or more of a) DMSO, b) one or more salts, or c) a base.

In some embodiments the loading agent is loaded into the platelets in the presence of an aqueous medium. In some embodiments the loading agent is loaded in the presence of a medium comprising DMSO. As an example, one embodiment of the methods herein comprises treating platelets with a drug and with an aqueous loading buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent, to form the cargo-loaded platelets. As an example, one embodiment of the methods herein comprises treating platelets with a drug and with a loading buffer comprising DMSO and comprising a salt, a base, a loading agent, and optionally ethanol, to form the cargo-loaded platelets.

In some embodiments the loading buffer, and/or the liquid medium, may comprise one or more salts selected from phosphate salts, sodium salts, potassium salts, calcium salts, magnesium salts, and any other salt that can be found in blood or blood products, or that is known to be useful in drying platelets, or any combination of two or more of these.

Preferably, these salts are present in the composition at an amount that is about the same as is found in whole blood.

In some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium for different durations at or at different temperatures from 15-45° C., or about 37° C. (cell to drug volume ratio of 1:2).

In some embodiments, the platelets form a suspension in a liquid medium at a concentration from 1,000 platelets/μL to 10,000,000 platelets/μL, such as 50,000 platelets/μL to 2,000,000 platelets/μL, such as 100,000 platelets/μL to 500,000 platelets/μL, such as 150,000 platelets/μL to 300,000 platelets/μL, such as 200,000 platelets/μL.

In some embodiments, one or more other components may be loaded in the platelets. In some embodiments, the one or more other components may be loaded concurrently with the drug. In some embodiments, the one or more other components may and the drug may be loaded sequentially in either order. Exemplary components may include Prostaglandin E1 or Prostacyclin and or EDTA/EGTA to prevent platelet aggregation and activation during the loading process. Additional non-limiting components may include, GR144053, FR171113, aspirin, MeSADP, PSB 0739, Cangrelor, Tirofiban, and MitoTEMPO. These components may be used alone or in combination with one another.

In some embodiments, the one or more other components that are loaded in the platelets comprise Prostaglandin E1 (PGE1) or Prostacyclin.

In some embodiments, the one or more other components that are loaded in the platelets do not comprise Prostaglandin E1 or Prostacyclin.

In some embodiments, the one or more other components that are loaded in the platelets comprise EGTA.

In some embodiments, the one or more other components that are loaded in the platelets do not comprise EGTA.

In some embodiments, the one or more other components that are loaded in the platelets comprise EDTA.

In some embodiments, the one or more other components that are loaded in the platelets do not comprise EDTA.

In some embodiments, other components may include imaging agents. For example, an imaging agent can include, but is not limited to a radioactive metal ion, a paramagnetic metal ion, a gamma-emitting radioactive halogen, a positron-emitting radioactive non-metal, a hyperpolarized NMR-active nucleus, a reporter suitable for in vivo optical imaging, or a beta-emitter suitable for intravascular detection. For example, a radioactive metal ion can include, but is not limited to, positron emitters such as 54Cu, 48V, 52Fe, 55Co, 94Tc or 68Ga; or gamma-emitters such as 171Tc, 111In, 113In, or 67Ga. For example, a paramagnetic metal ion can include, but is not limited to Gd(III), a Mn(II), a Cu(II), a Cr(III), a Fe(III), a Co(II), a Er(II), a Ni(II), a Eu(III) or a Dy(III), an element comprising an Fe element, a neodymium iron oxide (NdFeO3) or a dysprosium iron oxide (DyFeO3). For example, a paramagnetic metal ion can be chelated to a polypeptide or a monocrystalline nanoparticle. For example, a gamma-emitting radioactive halogen can include, but is not limited to 123I, 131I or 77Br. For example, a positron-emitting radioactive non-metal can include, but is not limited to 11C, 13N, 15O, 17F, 18F, 75Br, 76Br or 124I. For example, a hyperpolarized NMR-active nucleus can include, but is not limited to 13C, 15N, 19F, 29Si and 31P. For example, a reporter suitable for in vivo optical imaging can include, but is not limited to any moiety capable of detection either directly or indirectly in an optical imaging procedure. For example, the reporter suitable for in vivo optical imaging can be a light scatterer (e.g., a colored or uncolored particle), a light absorber or a light emitter. For example, the reporter can be any reporter that interacts with light in the electromagnetic spectrum with wavelengths from the ultraviolet to the near infrared. For example, organic chromophoric and fluorophoric reporters include groups having an extensive delocalized electron system, e.g. cyanines, merocyanines, indocyanines, phthalocyanines, naphthalocyanines, triphenylmethines, porphyrins, pyrilium dyes, thiapyrilium dyes, squarylium dyes, croconium dyes, azulenium dyes, indoanilines, benzophenoxazinium dyes, benzothiaphenothiazinium dyes, anthraquinones, napthoquinones, indathrenes, phthaloylacridones, trisphenoquinones, azo dyes, intramolecular and intermolecular charge-transfer dyes and dye complexes, tropones, tetrazines, b/s(dithiolene) complexes, bts(benzene-dithiolate) complexes, iodoaniline dyes, b/stS.O-dithiolene) complexes. For example, the reporter can be, but is not limited to a fluorescent, a bioluminescent, or chemiluminescent polypeptide. For example, a fluorescent or chemiluminescent polypeptide is a green florescent protein (GFP), a modified GFP to have different absorption/emission properties, a luciferase, an aequorin, an obelin, a mnemiopsin, a berovin, or a phenanthridinium ester. For example, a reporter can be, but is not limited to rare earth metals (e.g., europium, samarium, terbium, or dysprosium), or fluorescent nanocrystals (e.g., quantum dots). For example, a reporter may be a chromophore that can include, but is not limited to fluorescein, sulforhodamine 101 (Texas Red), rhodamine B, rhodamine 6G, rhodamine 19, indocyanine green, Cy2, Cy3, Cy3.5, Cy5, Cy5.5, Cy7, Marina Blue, Pacific Blue, Oregon Green 88, Oregon Green 514, tetramethylrhodamine, and Alexa Fluor 350, Alexa Fluor 430, Alexa Fluor 532, Alexa Fluor 546, Alexa Fluor 555, Alexa Fluor 568, Alexa Fluor 594, Alexa Fluor 633, Alexa Fluor 647, Alexa Fluor 660, Alexa Fluor 680, Alexa Fluor 700, and Alexa Fluor 750. For example, a beta-emitter can include, but is not limited to radio metals 67Cu, 89Sr, 90Y, 153 Sm, 185Re, 188Re or 192Ir, and non-metals 32P, 33P, 38S, 38Cl, 39Cl, 82Br and 83Br. In some embodiments, a drug loaded into platelets can be associated with gold or other equivalent metal particles (such as nanoparticles). For example, a metal particle system can include, but is not limited to gold nanoparticles (e.g., Nanogold™).

In some embodiments, the one or more imaging agents loaded concurrently with a drug is imaged using an imaging unit. The imaging unit can be configured to image the drug loaded platelets in vivo based on an expected property (e.g., optical property from the imaging agent) to be characterized. For example, imaging techniques (in vivo imaging using an imaging unit) that can be used, but are not limited to are: computer assisted tomography (CAT), magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), or bioluminescence imaging (BLI). Chen Z., et. al., (2014) have described various imaging techniques and which is incorporated by reference herein in its entirety.

In some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium for different durations. The step of incubating the platelets to load one or more cargo, such as a drug(s), includes incubating the platelets for a time suitable for loading, as long as the time, taken in conjunction with the temperature, is sufficient for the drug to come into contact with the platelets and, preferably, be incorporated, at least to some extent, into the platelets. For example, in some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium for at least about 5 minutes (mins) (e.g., at least about 20 mins, about 30 mins, about 1 hour (hr), about 2 hrs, about 3 hrs, about 4 hrs, about 5 hrs, about 6 hrs, about 7 hrs, about 8 hrs, about 9 hrs, about 10 hrs, about 12 hrs, about 16 hrs, about 20 hrs, about 24 hrs, about 30 hrs, about 36 hrs, about 42 hrs, about 48 hrs, or at least about 48 hrs. In some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium for no more than about 48 hrs (e.g., no more than about 20 mins, about 30 mins, about 1 hour (hr), about 2 hrs, about 3 hrs, about 4 hrs, about 5 hrs, about 6 hrs, about 7 hrs, about 8 hrs, about 9 hrs, about 10 hrs, about 12 hrs, about 16 hrs, about 20 hrs, about 24 hrs, about 30 hrs, about 36 hrs, or no more than about 42 hrs). In some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium from about 10 mins to about 48 hours (e.g., from about 20 mins to about 36 hrs, from about 30 mins to about 24 hrs, from about 1 hr to about 20 hrs, from about 2 hrs to about 16 hours, from about 10 mins to about 24 hours, from about 20 mins to about 12 hours, from about 30 mins to about 10 hrs, or from about 1 hr to about 6 hrs. In one embodiment, treating platelets, platelet derivatives, or thrombosomes with a drug, a liquid medium, and/or a buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent, to form the drug-loaded platelets comprises contacting the platelets, platelet derivatives, or thrombosomes with a drug, a liquid medium, and/or a buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent for a period of time, such as a period of 5 minutes to 48 hours, such as 2 hours.

In some embodiments, the drug-loaded platelets are prepared by incubating the platelets with the drug in the liquid medium at different temperatures. The step of incubating the platelets to load one or more cargo, such as a drug(s), includes incubating the platelets with the drug in the liquid medium at a temperature that, when selected in conjunction with the amount of time allotted for loading, is suitable for loading. In general, the platelets with the drug in the liquid medium are incubated at a suitable temperature (e.g., a temperature above freezing) for at least a sufficient time for the drug to come into contact with the platelets. In embodiments, incubation is conducted at 37° C. In certain embodiments, incubation is performed at 4° C. to 45° C., such as 15° C. to 42° C. For example, in embodiments, incubation is performed at 35° C. to 40° C. (e.g., 37° C.) for 110 to 130 (e.g., 120) minutes and for as long as 24-48 hours.

In some embodiments of a method of preparing drug-loaded platelets disclosed herein, the method further comprises acidifying the platelets, or pooled platelets, to a pH of about 6.0 to about 7.4, prior to a treating step disclosed herein. In some embodiments, the method comprises acidifying the platelets to a pH of about 6.5 to about 6.9. In some embodiments, the method comprises acidifying the platelets to a pH of about 6.6 to about 6.8. In some embodiments, the acidifying comprises adding to the pooled platelets a solution comprising Acid Citrate Dextrose.

In some embodiments, the platelets are isolated prior to a treating step. In some embodiments, the method further comprises isolating platelets by using centrifugation. In some embodiments, the centrifugation occurs at a relative centrifugal force (RCF) of about 800 g to about 2000 g. In some embodiments, the centrifugation occurs at relative centrifugal force (RCF) of about 1300 g to about 1800 g. In some embodiments, the centrifugation occurs at relative centrifugal force (RCF) of about 1500 g. In some embodiments, the centrifugation occurs for about 1 minute to about 60 minutes. In some embodiments, the centrifugation occurs for about 10 minutes to about 30 minutes. In some embodiments, the centrifugation occurs for about 30 minutes.

In some embodiments, the platelets are at a concentration from about 1,000 platelets/μl to about 10,000,000 platelets/μl. In some embodiments, the platelets are at a concentration from about 50,000 platelets/μl to about 4,000,000 platelets/μl. In some embodiments, the platelets are at a concentration from about 100,000 platelets/μl to about 300,000,000 platelets/μl. In some embodiments, the platelets are at a concentration from about 1,000,000 to about 2,000,000. In some embodiments, the platelets are at a concentration of about 200,000,000 platelets/μl.

In some embodiments, the buffer is a loading buffer comprising the components as listed in Table 1 herein. In some embodiments, the loading buffer comprises one or more salts, such as phosphate salts, sodium salts, potassium salts, calcium salts, magnesium salts, and any other salt that can be found in blood or blood products. Exemplary salts include sodium chloride (NaCl), potassium chloride (KCl), and combinations thereof. In some embodiments, the loading buffer includes from about 0.5 mM to about 100 mM of the one or more salts. In some embodiments, the loading buffer includes from about 1 mM to about 100 mM (e.g., about 2 mM to about 90 mM, about 2 mM to about 6 mM, about 50 mM to about 100 mM, about 60 mM to about 90 mM, about 70 to about 85 mM) about of the one or more salts. In some embodiments, the loading buffer includes about 5 mM, about 75 mM, or about 80 mM of the one or more salts.

In some embodiments, the loading buffer includes one or more buffers, e.g., N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), or sodium-bicarbonate (NaHCO₃). In some embodiments, the loading buffer includes from about 5 to about 100 mM of the one or more buffers. In some embodiments, the loading buffer includes from about 5 to about 50 mM (e.g., from about 5 mM to about 40 mM, from about 8 mM to about 30 mM, about 10 mM to about 25 mM) about of the one or more buffers. In some embodiments, the loading buffer includes about 10 mM, about 20 mM, about 25 mM, or about 30 mM of the one or more buffers.

In some embodiments, the loading buffer includes one or more saccharides, such as monosaccharides and disaccharides, including sucrose, maltose, trehalose, glucose, mannose, dextrose, and xylose. In some embodiments, the loading buffer includes from about 10 mM to about 1,000 mM of the one or more saccharides. In some embodiments, the loading buffer includes from about 50 to about 500 mM of the one or more saccharides. In embodiments, one or more saccharides is present in an amount of from 10 mM 10 to 500 mM. In some embodiments, one or more saccharides is present in an amount of from 50 mM to 200 mM. In embodiments, one or more saccharides is present in an amount from 100 mM to 150 mM.

In some embodiments, the loading buffer includes adding an organic solvent, such as ethanol, to the loading solution. In such a loading buffer, the solvent can range from about 0.1% (v/v) to about 5.0% (v/v), such as from about 0.3% (v/v) to about 3.0% (v/v), or from about 0.5% (v/v) to about 2% (v/v).

In some embodiments, the method further comprises incubating the drug in the presence of the loading buffer prior to the treatment step. In some embodiments, the method further comprises incubating the loading buffer and a solution comprising the drug and water at about 37° C. using different incubation periods. In some embodiments, the solution includes a concentration of about 1 nM to about 1000 mM of the drug. In some embodiments, the solution includes a concentration of about 10 nM to about 10 mM of the drug. In some embodiments, the solution includes a concentration of about 100 nM to 1 mM of the drug. In some embodiments, the solution includes a concentration of from about 10 mg/ml of water to about 100 mg/ml. In some embodiments, the solution includes a concentration of from about 20 mg/ml of water to about 80 mg/ml. In some embodiments, the solution includes a concentration of from about 40 mg/ml of water to about 60 mg/ml. In some embodiments, the incubation of the drug in the presence of the loading buffer is performed from about 1 minute to about 2 hours. In some embodiments, the incubation is performed at an incubation period of from about 5 minutes to about 1 hour. In some embodiments, the incubation is performed at an incubation period of from about 10 minutes to about 30 minutes. In some embodiments, the incubation is performed at an incubation period of about 20 minutes.

In some embodiments, the method further comprises mixing the platelets and the drug in the presence of the loading buffer at 37° C., using a platelet to drug volume ratio of 1:2. In some embodiments, the method further comprises incubating the platelets and the drug in the presence of the loading buffer at 37° C. using a platelet to drug volume ratio of 1:2, using different incubation periods. In some embodiments, the incubation is performed at an incubation period of from about 5 minutes to about 12 hours. In some embodiments, the incubation is performed at an incubation period of from about 10 minutes to about 6 hours. In some embodiments, the incubation is performed at an incubation period of from about 15 minutes to about 3 hours. In some embodiments, the incubation is performed at an incubation period of about 2 hours.

In some embodiments, the concentration of drug in the drug-loaded platelets is from about 1 nM to about 1000 mM. In some embodiments, the concentration of drug in the drug-loaded platelets is from about 10 nM to about 10 mM. In some embodiments, the concentration of drug in the drug-loaded platelets is from about 100 nM to 1 mM.

In some embodiments, the method further comprises drying the drug-loaded platelets. In some embodiments, the drying step comprises freeze-drying the drug-loaded platelets. In some embodiments, the method further comprises rehydrating the drug-loaded platelets obtained from the drying step.

In some embodiments, drug-loaded platelets are prepared by using any one of the methods provided herein.

In some embodiments, rehydrated drug-loaded platelets are prepared by any one method comprising rehydrating the drug-loaded platelets provided herein.

The drug-loaded platelets may be then used, for example, for therapeutic applications as disclosed herein. As another example, the drug-loaded platelets may, employed in functional assays. In some embodiments, the drug-loaded platelets are cold stored, cryopreserved, or lyophilized (to produce thrombosomes) prior to use in therapy or in functional assays.

Any known technique for drying platelets can be used in accordance with the present disclosure, as long as the technique can achieve a final residual moisture content of less than 5%. Preferably, the technique achieves a final residual moisture content of less than 2%, such as 1%, 0.5%, or 0.1%. Non-limiting examples of suitable techniques are freeze-drying (lyophilization) and spray-drying. A suitable lyophilization method is presented in Table A. Additional exemplary lyophilization methods can be found in U.S. Pat. Nos. 7,811,558, 8,486,617, and 8,097,403. An exemplary spray-drying method includes: combining nitrogen, as a drying gas, with a loading buffer according to the present disclosure, then introducing the mixture into GEA Mobile Minor spray dryer from GEA Processing Engineering, Inc. (Columbia Md., USA), which has a Two-Fluid Nozzle configuration, spray drying the mixture at an inlet temperature in the range of 150° C. to 190° C., an outlet temperature in the range of 65° C. to 100° C., an atomic rate in the range of 0.5 to 2.0 bars, an atomic rate in the range of 5 to 13 kg/hr, a nitrogen use in the range of 60 to 100 kg/hr, and a run time of 10 to 35 minutes. The final step in spray drying is preferentially collecting the dried mixture. The dried composition in some embodiments is stable for at least six months at temperatures that range from −20° C. or lower to 90° C. or higher.

TABLE A Exemplary Lyophilization Protocol Step Temp. Set Type Duration Pressure Set Freezing Step F1 −50° C.  Ramp Var N/A F2 −50° C.  Hold 3 Hrs N/A Vacuum Pulldown F3 −50° Hold Var N/A Primary Dry P1 −40° Hold 1.5 Hrs 0 mT P2 −35° Ramp 2 Hrs 0 mT P3 −25° Ramp 2 Hrs 0 mT P4 −17° C.  Ramp 2 Hrs 0 mT P5  0° C. Ramp 1.5 Hrs 0 mT P6 27° C. Ramp 1.5 Hrs 0 mT P7 27° C. Hold 16 Hrs 0 mT Secondary Dry S1 27° C. Hold >8 Hrs 0 mT

In some embodiments, the step of drying the drug-loaded platelets that are obtained as disclosed herein, such as the step of freeze-drying the drug-loaded platelets that are obtained as disclosed herein, comprises incubating the platelets with a lyophilizing agent (e.g., a non-reducing disaccharide. Accordingly, in some embodiments, the methods for preparing drug-loaded platelets further comprise incubating the drug-loaded platelets with a lyophilizing agent

In some embodiments the lyophilizing agent is a saccharide. In some embodiments the saccharide is a disaccharide, such as a non-reducing disaccharide).

In some embodiments, the platelets are incubated with a lyophilizing agent for a sufficient amount of time and at a suitable temperature to load the platelets with the lyophilizing agent. Non-limiting examples of suitable lyophilizing agents are saccharides, such as monosaccharides and disaccharides, including sucrose, maltose, trehalose, glucose (e.g., dextrose), mannose, and xylose. In some embodiments, non-limiting examples of lyophilizing agent include serum albumin, dextran, polyvinyl pyrolidone (PVP), starch, and hydroxyethyl starch (HES). In some embodiments, exemplary lyophilizing agents can include a high molecular weight polymer, into the loading composition. By “high molecular weight” it is meant a polymer having an average molecular weight of about or above 70 kDa. Non-limiting examples are polymers of sucrose and epichlorohydrin. In some embodiments, the lyophilizing agent is polysucrose. Although any amount of high molecular weight polymer can be used as a lyophilizing agent, it is preferred that an amount be used that achieves a final concentration of about 3% to 10% (w/v), such as 3% to 7%, for example 6%.

In some embodiments, the process for preparing a composition includes adding an organic solvent, such as ethanol, to the loading solution. In such a loading solution, the solvent can range from 0.1% to 5.0% (v/v).

Within the process provided herein for making the compositions provided herein, addition of the lyophilizing agent can be the last step prior to drying. However, in some embodiments, the lyophilizing agent is added at the same time or before the drug, the cryoprotectant, or other components of the loading composition. In some embodiments, the lyophilizing agent is added to the loading solution, thoroughly mixed to form a drying solution, dispensed into a drying vessel (e.g., a glass or plastic serum vial, a lyophilization bag), and subjected to conditions that allow for drying of the solution to form a dried composition.

An exemplary saccharide for use in the compositions disclosed herein is trehalose. Regardless of the identity of the saccharide, it can be present in the composition in any suitable amount. For example, it can be present in an amount of 1 mM to 1 M. In some embodiments, it is present in an amount of from 10 mM 10 to 500 mM. In some embodiments, it is present in an amount of from 20 mM to 200 mM. In some embodiments, it is present in an amount from 40 mM to 100 mM. In various embodiments, the saccharide is present in different specific concentrations within the ranges recited above, and one of skill in the art can immediately understand the various concentrations without the need to specifically recite each herein. Where more than one saccharide is present in the composition, each saccharide can be present in an amount according to the ranges and particular concentrations recited above.

The step of incubating the platelets to load them with a cryoprotectant or as a lyophilizing agent includes incubating the platelets for a time suitable for loading, as long as the time, taken in conjunction with the temperature, is sufficient for the cryoprotectant or lyophilizing agent to come into contact with the platelets and, preferably, be incorporated, at least to some extent, into the platelets. In some embodiments, incubation is carried out for about 1 minute to about 180 minutes or longer.

The step of incubating the platelets to load them with a cryoprotectant or lyophilizing agent includes incubating the platelets and the cryoprotectant at a temperature that, when selected in conjunction with the amount of time allotted for loading, is suitable for loading. In general, the composition is incubated at a temperature above freezing for at least a sufficient time for the cryoprotectant or lyophilizing agent to come into contact with the platelets. In embodiments, incubation is conducted at 37° C. In certain embodiments, incubation is performed at 20° C. to 42° C. For example, in embodiments, incubation is performed at 35° C. to 40° C. (e.g., 37° C.) for 110 to 130 (e.g., 120) minutes.

In various embodiments, the bag is a gas-permeable bag configured to allow gases to pass through at least a portion or all portions of the bag during the processing. The gas-permeable bag can allow for the exchange of gas within the interior of the bag with atmospheric gas present in the surrounding environment. The gas-permeable bag can be permeable to gases, such as oxygen, nitrogen, water, air, hydrogen, and carbon dioxide, allowing gas exchange to occur in the compositions provided herein. In some embodiments, the gas-permeable bag allows for the removal of some of the carbon dioxide present within an interior of the bag by allowing the carbon dioxide to permeate through its wall. In some embodiments, the release of carbon dioxide from the bag can be advantageous to maintaining a desired pH level of the composition contained within the bag.

In some embodiments, the container of the process herein is a gas-permeable container that is closed or sealed. In some embodiments, the container is a container that is closed or sealed and a portion of which is gas-permeable. In some embodiments, the surface area of a gas-permeable portion of a closed or sealed container (e.g., bag) relative to the volume of the product being contained in the container (hereinafter referred to as the “SA/V ratio”) can be adjusted to improve pH maintenance of the compositions provided herein. For example, in some embodiments, the SA/V ratio of the container can be at least about 2.0 mL/cm² (e.g., at least about 2.1 mL/cm², at least about 2.2 mL/cm², at least about 2.3 mL/cm², at least about 2.4 mL/cm², at least about 2.5 mL/cm², at least about 2.6 mL/cm², at least about 2.7 mL/cm², at least about 2.8 mL/cm², at least about 2.9 mL/cm², at least about 3.0 mL/cm², at least about 3.1 mL/cm², at least about 3.2 mL/cm², at least about 3.3 mL/cm², at least about 3.4 mL/cm², at least about 3.5 mL/cm², at least about 3.6 mL/cm², at least about 3.7 mL/cm², at least about 3.8 mL/cm², at least about 3.9 mL/cm², at least about 4.0 mL/cm², at least about 4.1 mL/cm², at least about 4.2 mL/cm², at least about 4.3 mL/cm², at least about 4.4 mL/cm², at least about 4.5 mL/cm², at least about 4.6 mL/cm², at least about 4.7 mL/cm², at least about 4.8 mL/cm², at least about 4.9 mL/cm², or at least about 5.0 mL/cm². In some embodiments, the SA/V ratio of the container can be at most about 10.0 mL/cm² (e.g., at most about 9.9 mL/cm², at most about 9.8 mL/cm², at most about 9.7 mL/cm², at most about 9.6 mL/cm², at most about 9.5 mL/cm², at most about 9.4 mL/cm², at most about 9.3 mL/cm², at most about 9.2 mL/cm², at most about 9.1 mL/cm², at most about 9.0 mL/cm², at most about 8.9 mL/cm², at most about 8.8 mL/cm², at most about 8.7 mL/cm², at most about 8.6, mL/cm² at most about 8.5 mL/cm², at most about 8.4 mL/cm², at most about 8.3 mL/cm², at most about 8.2 mL/cm², at most about 8.1 mL/cm², at most about 8.0 mL/cm², at most about 7.9 mL/cm², at most about 7.8 mL/cm², at most about 7.7 mL/cm², at most about 7.6 mL/cm², at most about 7.5 mL/cm², at most about 7.4 mL/cm², at most about 7.3 mL/cm², at most about 7.2 mL/cm², at most about 7.1 mL/cm², at most about 6.9 mL/cm², at most about 6.8 mL/cm², at most about 6.7 mL/cm², at most about 6.6 mL/cm², at most about 6.5 mL/cm², at most about 6.4 mL/cm², at most about 6.3 mL/cm², at most about 6.2 mL/cm², at most about 6.1 mL/cm², at most about 6.0 mL/cm², at most about 5.9 mL/cm², at most about 5.8 mL/cm², at most about 5.7 mL/cm², at most about 5.6 mL/cm², at most about 5.5 mL/cm², at most about 5.4 mL/cm², at most about 5.3 mL/cm², at most about 5.2 mL/cm², at most about 5.1 mL/cm², at most about 5.0 mL/cm², at most about 4.9 mL/cm², at most about 4.8 mL/cm², at most about 4.7 mL/cm², at most about 4.6 mL/cm², at most about 4.5 mL/cm², at most about 4.4 mL/cm², at most about 4.3 mL/cm², at most about 4.2 mL/cm², at most about 4.1 mL/cm², or at most about 4.0 mL/cm². In some embodiments, the SA/V ratio of the container can range from about 2.0 to about 10.0 mL/cm² (e.g., from about 2.1 mL/cm² to about 9.9 mL/cm², from about 2.2 mL/cm² to about 9.8 mL/cm², from about 2.3 mL/cm² to about 9.7 mL/cm², from about 2.4 mL/cm² to about 9.6 mL/cm², from about 2.5 mL/cm² to about 9.5 mL/cm², from about 2.6 mL/cm² to about 9.4 mL/cm², from about 2.7 mL/cm² to about 9.3 mL/cm², from about 2.8 mL/cm² to about 9.2 mL/cm², from about 2.9 mL/cm² to about 9.1 mL/cm², from about 3.0 mL/cm² to about 9.0 mL/cm², from about 3.1 mL/cm² to about 8.9 mL/cm², from about 3.2 mL/cm² to about 8.8 mL/cm², from about 3.3 mL/cm² to about 8.7 mL/cm², from about 3.4 mL/cm² to about 8.6 mL/cm², from about 3.5 mL/cm² to about 8.5 mL/cm², from about 3.6 mL/cm² to about 8.4 mL/cm², from about 3.7 mL/cm² to about 8.3 mL/cm², from about 3.8 mL/cm² to about 8.2 mL/cm², from about 3.9 mL/cm² to about 8.1 mL/cm², from about 4.0 mL/cm² to about 8.0 mL/cm², from about 4.1 mL/cm² to about 7.9 mL/cm², from about 4.2 mL/cm² to about 7.8 mL/cm², from about 4.3 mL/cm² to about 7.7 mL/cm², from about 4.4 mL/cm² to about 7.6 mL/cm², from about 4.5 mL/cm² to about 7.5 mL/cm², from about 4.6 mL/cm² to about 7.4 mL/cm², from about 4.7 mL/cm² to about 7.3 mL/cm², from about 4.8 mL/cm² to about 7.2 mL/cm², from about 4.9 mL/cm² to about 7.1 mL/cm², from about 5.0 mL/cm² to about 6.9 mL/cm², from about 5.1 mL/cm² to about 6.8 mL/cm², from about 5.2 mL/cm² to about 6.7 mL/cm², from about 5.3 mL/cm² to about 6.6 mL/cm², from about 5.4 mL/cm² to about 6.5 mL/cm², from about 5.5 mL/cm² to about 6.4 mL/cm², from about 5.6 mL/cm² to about 6.3 mL/cm², from about 5.7 mL/cm² to about 6.2 mL/cm², or from about 5.8 mL/cm² to about 6.1 mL/cm².

Gas-permeable closed containers (e.g., bags) or portions thereof can be made of one or more various gas-permeable materials. In some embodiments, the gas-permeable bag can be made of one or more polymers including fluoropolymers (such as polytetrafluoroethylene (PTFE) and perfluoroalkoxy (PFA) polymers), polyolefins (such as low-density polyethylene (LDPE), high-density polyethylene (HDPE)), fluorinated ethylene propylene (FEP), polystyrene, polyvinylchloride (PVC), silicone, and any combinations thereof.

In some embodiments the lyophilizing agent as disclosed herein may be a high molecular weight polymer. By “high molecular weight” it is meant a polymer having an average molecular weight of about or above 70 kDa and up to 1,000,000 kDa Non-limiting examples are polymers of sucrose and epichlorohydrin (polysucrose). Although any amount of high molecular weight polymer can be used, it is preferred that an amount be used that achieves a final concentration of about 3% to 10% (w/v), such as 3% to 7%, for example 6%. Other non-limiting examples of lyoprotectants are serum albumin, dextran, polyvinyl pyrrolidone (PVP), starch, and hydroxyethyl starch (HES).

In some embodiments, the loading buffer comprises an organic solvent, such as an alcohol (e.g., ethanol). In such a loading buffer, the amount of solvent can range from 0.1% to 5.0% (v/v).

In some embodiments the drug-loaded platelets prepared as disclosed herein have a storage stability that is at least about equal to that of the platelets prior to the loading of the drug.

The loading buffer may be any buffer that is non-toxic to the platelets and provides adequate buffering capacity to the solution at the temperatures at which the solution will be exposed during the process provided herein. Thus, the buffer may comprise any of the known biologically compatible buffers available commercially, such as phosphate buffers, such as phosphate buffered saline (PBS), bicarbonate/carbonic acid, such as sodium-bicarbonate buffer, N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES), and tris-based buffers, such as tris-buffered saline (TBS). Likewise, it may comprise one or more of the following buffers: propane-1,2,3-tricarboxylic (tricarballylic); benzenepentacarboxylic; maleic; 2,2-dimethylsuccinic; EDTA; 3,3-dimethylglutaric; bis(2-hydroxyethyl)imino-tris(hydroxymethyl)-methane (BIS-TRIS); benzenehexacarboxylic (mellitic); N-(2-acetamido)imino-diacetic acid (ADA); butane-1,2,3,4-tetracarboxylic; pyrophosphoric; 1,1-cyclopentanediacetic (3,3 tetramethylene-glutaric acid); piperazine-1,4-bis-(2-ethanesulfonic acid) (PIPES); N-(2-acetamido)-2-amnoethanesulfonic acid (ACES); 1,1-cyclohexanediacetic; 3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid (EMTA; ENDCA); imidazole; 2-(aminoethyl)trimethylammonium chloride (CHOLAMINE); N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES); 2-methylpropane-1,2,3-triscarboxylic (beta-methyltricarballylic); 2-(N-morpholino)propane-sulfonic acid (MOPS); phosphoric; and N-tris(hydroxymethyl)methyl-2-amminoethane sulfonic acid (TES).

Flow cytometry is used to obtain a relative quantification of loading efficiency by measuring the mean fluorescence intensity of the drug in the drug-loaded platelets. Platelets are evaluated for functionality by ADP and/or TRAP stimulation post-loading. In some embodiments, platelets can be evaluated for functionality by other platelet agonists known in the art.

In some embodiments the drug-loaded platelets are lyophilized. In some embodiments the drug-loaded platelets are cryopreserved.

In some embodiments the drug-loaded platelets retain the loaded drug upon rehydration and release the drug upon stimulation by endogenous platelet activators.

In some embodiments the dried platelets (such as freeze-dried platelets) retain the loaded drug upon rehydration and release the drug upon stimulation by endogenous platelet activators. In some embodiments at least about 10%, such as at least about 20%, such as at least about 30% of the drug is retained. In some embodiments from about 10% to about 20%, such as from about 20% to about 30% of the drug is retained.

Another example is of a drug that may be loaded in a platelet is vancomycin.

Various agents and/or procedures may be used to load the platelets with a drug. In some embodiments, the platelets are loaded with a liposomal formulation of the drug. In some embodiments, the drug is not comprised in a liposomal formulation. In some embodiments, the platelets are loaded with a drug previously incubated with a cell penetrating peptide. In some embodiments, when the drug is incubated with a cell penetrating peptide the cell penetrating peptide can be PEP-1. In some embodiments, the platelets are loaded with a drug conjugated with a cell penetrating peptide. In some embodiments, when the drug is conjugated with a cell penetrating peptide the cell penetrating peptide can be a TAT peptide. In some embodiments, the platelets are loaded with a drug previously incubated with a cationic lipid such as lipofectamine.

In some embodiments, the platelets are loaded with the drug in the presence of a detergent. For example, the detergent may be saponin.

In some embodiments, the platelets are loaded by a process comprising endocytosis.

In some embodiments, the platelets are loaded by a process comprising electroporation. Electrical pulses increase the porosity of the cell membrane and can lead to improved loading of materials (e.g., a drug)

In some embodiments, the platelets are loaded by a process comprising transduction.

In some embodiments, the platelets are loaded by a process comprising sonoporation. Sonoporation increases the porosity of cell membranes via ultrasound.

In some embodiments, the platelets are loaded by a process comprising osmotic hypertonic/hypotonic loading/hypotonic shock. Hypotonic shock uses a solution with lower osmotic pressure to induce cell swelling leading to membrane permeability. Hypertonic shock may increase platelet loading of cryoprotectants or lyoprotectants (e.g., trehalose) (Zhou X., et. al., Loading Trehalose into Red Blood Cells by Improved Hypotonic Method, Cell Preservation Technology, 6(2), https://doi.org/10.1089/cpt.2008.0001 (2008) which is herein incorporated by reference). Additionally and alternatively, hypotonic shock may allow the uptake and internalization of large and/or charged molecules through passive means, such as, endocytosis, micropinocytosis, and/or diffusion.

In some embodiments, hypertonic/hypotonic loading comprises an osmotic gradient to drive pore formation in the platelet's cell membrane and influx cargo intracellularly. In some embodiments, platelets may be isolated (e.g., centrifuged) and resuspended in a hypertonic pre-treatment solution. In some embodiments, the pre-treatment solution can be a carbohydrate in a buffer. For example, the carbohydrate can be a monosaccharide. In a non-limiting way, suitable monosaccharides include: fructose (levulose), galactose, ribose, deoxyribose, xylose, mannose, and fucose. In some embodiments, the carbohydrate can be a disaccharide. In a non-limiting way, suitable disaccharides include: sucrose, lactose, maltose, lactulose, trehalose, and cellobiose. In some embodiments, the carbohydrate can be dextrose in PBS buffer. In some embodiments, the percent dextrose can be about 15% dextrose in PBS to about 20% dextrose in PBS. In some embodiments, the percent dextrose in PBS can be about 16%, about 17%, about 18%, and about 19% dextrose in PBS. In some embodiments, the platelets can be pre-treated for about 10 minutes to about 60 minutes. In some embodiments, the platelets can be pre-treated for about 20, about 30, about 40, and about 50 minutes.

TABLE 1 Measured and theoretical osmolarity of each of the hypertonic “pre-treatment” solutions. The theoretical osmotic gradient is the difference in osmolarity between the loading solution and the hypertonic “pre-treatment” solution. Osmolarity of Hypertonic “Pre-treatment” Solutions PBS/Glucose Solution Theoretical Measured Theoretical (% Dextrose) Osmolarity Osmolarity % Diff. Osmotic Gradient 0 300 307 2.3% 0 2.5 439 449 2.3% 142 5 578 581 0.6% 274 10 855 873 2.1% 566 15 1133 1168 3.1% 861

In some embodiments, the pre-treatment solutions can have a high osmolarity relative to blood plasma (e.g., about 300mOsmoles). For example, the pre-treatment solutions can have a high osmolarity relative to blood plasma (e.g., about 300mOsmoles), such as an osmolarity of about 400 mOsmoles to about 1200 mOsmoles. In some embodiments, the pre-treatment osmolarity of about 500 mOsmoles, about 600 mOsmoles, about 700 mOsmoles, about 800 mOsmoles, about 900 mOsmoles, about 1,000 mOsmoles, and about 1,100 mOsmoles.

In some embodiments, after pre-treatment the platelets are allowed to equilibrate for about 10 minutes to about 120 minutes. In some embodiments, the platelets are allowed to equilibrate for about 20, about 30, about 40, about 50, about 60, about 70, about 80, about 90, about 100, and about 110 minutes.

In some embodiments, after the platelets have been allowed to equilibrate post incubation in the pre-treatment solution, the platelets are isolated (e.g., centrifuged) and resuspended in loading buffer that is approximately isotonic with blood plasma and contains cargo (e.g., any cargo described herein). As a result, an osmotic pressure gradient is established that causes pore formation in the platelet cellular membrane and influx of the solution containing cargo.

In some embodiments, the solutes in the hypertonic solution can be, in a non-limiting way, salts, low-molecular weight sugars (e.g., monosaccharides, disaccharides), or low molecular weight inert hydrophilic polymers.

In some embodiments, hypertonic/hypotonic loading is used to load water soluble cargo.

In some embodiments, the platelets are loaded by a process comprising the use of Transfection Reagents (also described in WO2014118817A2, incorporated by reference herein in its entirety).

Exemplary protocols that employ the foregoing agents or procedures are shown below:

A liposome is a vesicle made of phospholipid bilayer. This vesicle can be designed to encapsulate drug of interest, which is delivered inside a cell following the fusion of vesicle and cell membrane.

Endocytosis is a process through which a cell takes in material from its surroundings. The cell invaginates its plasma membrane to wrap around fluid or particles in its immediate environment. The internalized vesicle buds off from the plasma membrane and remains inside the cell.

Co-incubation of platelets with drug of interest occurs at 37° C. for 1-4 hours during which drug is loaded into platelets via endocytosis. Loaded platelets may then be lyophilized to make Thrombosomes. Loaded drug is detected via flow cytometry or fluorescence microscopy, provided drug is fluorescently tagged or is itself fluorescent. Endocytic inhibitors such as amiloride (1 mM), phenylarsine oxide (10 μM), cytochalasin D (4 μM), or dynasore (25 μM) can be used to confirm that platelet loading is achieved by endocytosis.

Pep-1 is a 21 amino acid cell penetrating peptide with a C-terminal cysteamine group that shuttles cargo such as proteins or peptides into target cells. Pep-1 consists of a hydrophobic domain linked to a hydrophilic domain. The hydrophobic, tryptophan-rich domain can associate with a target cell membrane and the hydrophobic domains of the cargo protein.

The Pep-1 and the cargo protein are complexed by co-incubation at 37° C. for 30 minutes. The Pep-1:protein complex is incubated with platelets at 37° C. for at minimum 1 hour to allow Pep-1 mediated loading of protein cargo into the platelet. Platelets are washed by centrifugation to remove cell-free Pep-1:protein complex. Loaded platelets may then be lyophilized to make Thrombosomes. Platelets that have accumulated Pep-1 can be detected via flow cytometry or fluorescence microscopy if a fluorescent tag is attached to the C-terminus cysteamine of Pep-1. If the cargo protein is fluorescently labeled, then platelets containing this cargo may also be detected using flow cytometry or fluorescence microscopy.

The HIV TAT protein is another example of a cell penetrating peptide. The TAT protein includes between 86 and 101 amino acids depending on the subtype. TAT is a regulatory protein that enhances the viral transcription efficiency. TAT also contains a protein transduction domain which functions as a cell-penetrating domain allowing Tat to cross cellular membranes.

The HIV Tat protein is another example of a cell penetrating peptide. The TAT protein includes between 86 and 101 amino acids depending on the subtype. TAT is a regulatory protein that enhances the viral transcription efficiency. TAT also contains a protein transduction domain which functions as a cell-penetrating domain allowing TAT to cross cellular membranes.

Lipofectamine is a cationic lipid; the Lipofectamine positively charged head group interacts with the negatively charged phosphate backbone of nucleic acids to facilitate transfection. Cellular internalization of the nucleic acid is achieved by incubating cells with the complexed Lipofectamine and nucleic acid.

Prepare the Lipofectamine and nucleic acid complex in aqueous buffer at room temperature. Incubate the complexed Lipofectamine and nucleic acid with platelets for 2-3 hours. Transfected platelets may be lyophilized to create Thrombosomes. Fluorescently labeled nucleic acid can be detected via flow cytometry and visualized using fluorescence microscopy. This method of loading is applicable to both RNA and DNA.

Saponin is a detergent which can be used, under optimal concentration, to remove cholesterol from cell membrane and thereby increase the permeability of plasma membranes. Cells treated with saponin are permeable to molecules that would otherwise be excluded by the plasma membrane.

Incubate platelets with 1-20 μg/ml of saponin at 37° C. to permeabilize platelet cell membranes. Incubate saponin permeabilized platelets with drug at 37° C. for 2-4 hours to allow for loading. Loaded platelets may be lyophilized to make Thrombosomes. Drug can be detected using flow cytometry or fluorescence microscopy if fluorescently tagged. In order to confirm that saponin treatment permeabilized platelet membrane, stimulate platelets with inositol 1,4,5-triphosphate (IP3). IP3 stimulation of platelets lead to a cascade of reactions that generate phosphorylated substrates for protein kinase C, and this ultimately leads to release of 5-HT from dense granules.

An electroporation machine generates electrical pulses which facilitate formation of transient openings in plasma membranes. The increased plasma membrane permeability allows entry of large and/or charged cargo that would otherwise not enter the cell due to membrane barrier.

Perform electroporation of platelets in the presence of desired cargo. Cargos of interest can be detected by flow cytometry and fluorescence microscopy if they are fluorescently tagged.

The influx cell loading strategy harnesses osmosis to load cells with water soluble, polar compounds. Cells are initially placed in a hypertonic solution containing drug of interest. In this hypertonic solution, water will move out of the cell into solution while drug will move into the cell via pinocytosis. Following that, cells are placed in a hypotonic solution in which water will enter the cell, lysing the pinocytic vesicles and thereby releasing drug into the cytosol.

Incubate platelets in hypertonic loading medium containing drug compound at 37° C. for at least 1 hour. Isolate loaded platelets from solution via centrifugation, resuspend platelets in hypotonic lysis medium, and incubate at 37° C. Pinocytic vesicles will burst and release drug into the cytosol. Fluorescently labeled drug can be visualized using fluorescence microscopy to confirm internalization. Flow cytometry may be performed to quantify drug load per cell for fluorescent drug.

Viral vectors are commonly used for transduction of cells. The host cell is driven by the viral vector to express the protein of interest at high load.

Use lentiviral vector to transfect 293T cells to generate pseudovirus, which is collected from the supernatant of this cell culture. The pseudovirus is then used to transduce megakaryocytes. Inside the transduced megakaryocyte, viral core plasmid containing cytomegalovirus promotor drives overexpression of the protein of interest, which gets packaged into platelets that bud off from transduced megakaryocytes.

Human platelets express FcγRIIA receptor which binds to the Fc region of IgG and facilitates internalization of IgG immune complexes. This method of loading platelets provides a route for delivery of therapeutic antibodies.

Incubate fluorescently labeled IgG at 62° C. for 20 minutes to prepare IgG immune complexes. Incubate IgG immune complexes with platelets for 1 hour at 4° C. to allow cells to bind immune complexes. Next, incubate immune complex-bound platelets at 37° C. to allow internalization of immune complexes. Flow cytometry can detect internalized fluorophore labeled IgG immune complexes. An anti-IgG-PE antibody specific for immune complexes can be used to identify surface bound, but not internalized, IgG-FITC immune complex.

In FIG. 1, platelets were incubated in the presence of saponin at a concentration of either 5 μg/mL or 7.5 μg/mL to permeabilize platelet cell membranes. 1,4,5-triphosphate (IP3) was added at the time points indicated. Saponin-mediated permeabilization of platelets was measured using standard light transmission aggregometry (LTA). The data of FIG. 1 show that saponin permeabilizes platelet cell membranes in a concentration-dependent manner.

In FIG. 2, platelets were incubated in the presence of saponin at the concentrations indicated on the x-axis using Hepes modified Tyrode's albumin (HMTA). Cells only bars represent samples in which the platelets were incubated in the absence of Lucifer yellow. Isotype control bars represent samples in which the platelets were incubated in the presence of a reference antibody. Lucifer Yellow bars represent samples in which the platelets were incubated in the presence of Lucifer yellow. Fluorescence was measured using flow cytometry. These data show that saponin increases permeabilization of platelet cell membranes in a concentration-dependent manner.

In FIG. 3, platelets were separately incubated for four hours with fluorescently-labeled: BODIPY-vancomycin, FITC-bovine IgG, FITC-Fab2, FITC-albumin, or FITC dextran.

The fluorescently-labeled molecules were loaded into platelets via fluid phase endocytosis. Flow cytometry was performed to determine endocytotic loading efficiency. These data show that fluorescently-labeled vancomycin was efficiently loaded into platelets via fluid phase endocytosis.

In FIG. 4, platelets were separately incubated with fluorescently-labeled BODIPY-vancomycin for zero, two, or four hours in the presence or absence of trehalose. The fluorescently-labeled BODIPY-vancomycin was loaded into platelets via fluid phase endocytosis. Flow cytometry was performed to determine endocytotic loading efficiency. These data show that fluorescently-labeled vancomycin was more efficiently loaded into platelets via fluid phase endocytosis at four hours in the presence of trehalose than in the absence of trehalose.

Examples of drugs and of loading agents are as follows:

Osmotic hypertonic/ Cell penetrating hypotonic Endocytosis peptide loading BODIPY-vancomycin BODIPY-vancomycin BODIPY- vancomycin; BODIPY-vancomycin and Dextran 10K Dextran 10K ristocetin Dextran 10K Dextran 3K Dextran 3K Dextran 500K Dextran 500K Dextran 500K FITC-Albumin FITC-albumin FITC-albumin FITC-Bovine IGG FITC-Bovine IGG FMLP FITC-F(ab)₂ FITC-F(ab)₂ Histone H1 Histone H1 FMLP Lucifer Yellow Lucifer yellow-slow uptake Histone H1 PE (PHYCOERYTRIN) PE Lucifer yellow Rabbit IGG Rabbit IGG PE Soybean Trypsin Inhibitor Soybean Trypsin Inhibitor Rabbit IGG Soybean Trypsin Inhibitor

The table below provides examples of various types of drugs that may be loaded into the platelets, such as antibiotics like vancomycin and ristocetin; antibodies such as rabbit IGG; antibody fragments such as F(ab)₂; peptides such as FMLP; protease inhibitors such as Soybean Trypsin Inhibitor; and Lucifer yellow. Similarly, the table below provides examples of various types of loading agents, such as albumin or such as dextrans having various molecular weights.

More particular examples are as follows:

Osmotic hypertonic/ Cell penetrating hypotonic Endocytosis peptide loading BODIPY-vancomycin BODIPY-vancomycin BODIPY- vancomycin; FITC-Bovine IGG Dextran 500K Dextran 10K Rabbit IGG FITC-albumin Dextran 3K FITC-Bovine FMLP FMLP Rabbit IGG Soybean Trypsin Inhibitor

In some embodiments the drug is vancomycin. In some embodiments where the drug is vancomycin, the drug is labeled with BODIPY (boron-dipyrromethene or 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene). In some embodiments, the loading step comprises the use of dextran as a lyophilizing agent. In some embodiments the drug is an antibody. In some embodiments when the drug is an antibody, the drug is labeled with FITC (fluorescein isothiocyanate or 3′,6′-dihydroxy-6-isothiocyanatospiro[2-benzofuran-3,9′-xanthene]-1-one). In some embodiments, the drug is soybean trypsin inhibitor.

In some embodiments, drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes may shield the drug from exposure in circulation, thereby reducing or eliminating systemic toxicity (e.g. cardiotoxicity) associated with the drug. In some embodiments, drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes may also protect the drug from metabolic degradation or inactivation. In some embodiments, drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes may be used in any therapeutic setting in which expedited healing process is required or advantageous.

In some embodiments, provided herein is a method of treating a disease as disclosed herein, comprising administering drug-loaded platelets, drug-loaded platelet derivatives, or drug-loaded thrombosomes as disclosed herein. In some embodiments, provided herein is a method of treating a disease as disclosed herein, comprising administering cold stored, room temperature stored, cryopreserved thawed, rehydrated, and/or lyophilized platelets, platelet derivatives, or thrombosomes as disclosed herein. In some embodiments, the disease is, Traumatic Brain injury. In some embodiments, the disease is, ITP. In some embodiments, the disease is TTP.

Examples of diseases (therapeutic indications) that may be treated with the drug-loaded platelets are as follows:

Therapeutic indications Colitis Corynebacterium Enterococci Methicillin - resistant Staphylococci aureus Streptococcus pneumoniae Viridans streptococci Staphylococcal infection Chronic inflammatory demyelinating polyneuropathy Guillain - Barre syndrome Immune Thrombocytopenia Kawasaki disease Lupus Multiple Sclerosis Myasthenia gravis Myositis Thrombosis Crohn's disease Macular degeneration Albuminaemia Burns (>30% body surface area, after first 24 hours) Cardiac surgery (last line of treatment) Cirrhosis with refractory ascites Haemorrhagic shock (when patient not responsive to crystalloids/colloids) Hepatorenal syndrome (used in combination with vasoconstrictive drugs) Nephrotic syndrome (for patient with albumin <2 g/dL with hypovolaemia and/or pulmonary edema) Organ transplantation Paracentesis Spontaneous bacterial peritonitis (in addition with antibiotics) Hypovolemia Iron deficiency (intramuscular injection of ⁵⁹Fe iron dextran, INFeD. For patients who do not respond to or unable to take oral iron supplement) Fluid resuscitation in shock Aneurysms Artherosclerosis Cardiovascular diseases (post - myocardial infarction remodeling, cardiac regeneration, cardiac fibrosis, viral myocarditis, cardiac hypertrophy, pathological cardiac remodeling) Genetic disorders Infectious diseases Metabolic diseases Opthalmic conditions (retinal angiogenesis) Pulmonary hypertension

Examples of cargo and therapeutic indications for cargo(s) to be loaded into platelets are as follows:

Cargo Therapeutic indications Vancomycin (antibiotic) Colitis Corynebacterium Enterococci Methicillin - resistant Staphylococci aureus Streptococcus pneumoniae Viridans streptococci V ancomycin-Ristocetin Staphylococcal infection (antibiotic) IgG (antibody) Chronic inflammatory demyelinating polyneuropathy Guillain - Barre syndrome Immune Thrombocytopenia Kawasaki disease Lupus Multiple Sclerosis Myasthenia gravis Myositis Fab'2 (fragment of antibody) Abciximab (Reopro) used for clot prevention in angioplasty Certolizumab pegol (Cimzia) treat moderate to severe Crohn's disease Ranibizumab (Lucentis) treat macular degeneration Albumin (carrier protein) Albuminaemia Burns (>30% body surface area, after first 24 hours) Cardiac surgery (last line of treatment) Cirrhosis with refractory ascites Haemorrhagic shock (when patient not responsive to crystalloids/colloids) Hepatorenal syndrome (used in combination with vasoconstrictive drugs) Nephrotic syndrome (for patient with albumin <2 g/dL with hypovolaemia and/or pulmonary edema) Organ transplantation Paracentesis Spontaneous bacterial peritonitis (in addition with antibiotics) Dextran Hypovolemia Iron deficiency (intramuscular injection of ⁵⁹Fe iron dextran, INFeD. For patients who do not respond to or unable to take oral iron supplement) Fluid resuscitation in shock

In some embodiments, a drug may be fluorescent or labeled with a fluorescent moiety. For such a fluorescent or labeled drug, a correlation may be established between the fluorescence intensity and its concentration, and such a correlation may then be used to determine the concentration of the drug over a range of values.

Examples of loading buffer that may be used are shown in Tables 1-4:

TABLE 1 Loading Buffer Concentration Component (mM unless otherwise specified) NaCl 75.0 KCl 4.8 HEPES 9.5 NaHCO3 12.0 Dextrose 3 Trehalose 100 Ethanol 1% (v/v)

-   -   Table 1. Loading Buffer is used to load platelets via         endocytosis at 37° C. with gentle agitation as sample is placed         on a rocker. Adjust pH to 6.6-6.8

TABLE 2 Buffer A Concentration Component (mM unless specified otherwise) CaCl₂ 1.8 MgCl₂ 1.1 KCl 2.7 NaCl 137 NaH₂PO₄ 0.4 HEPES 10 D-glucose 5.6 pH 6.5

-   -   Table 2. Buffer A is used for loading platelets with liposome         encapsulated drug. Incubation done at 37° C. with gentle         agitation as sample is placed on a rocker.

TABLE 3 Buffer B Concentration Component (mM unless otherwise specified) Buffer and Salts Table 4 (below) BSA 0.35% Dextrose 5 pH 7.4

-   -   Table 3. Buffer B is used when incubating platelets with         fluorophore conjugated antibodies for flow cytometry. This         incubation is done at room temperature in the dark.     -   Albumin is an optional component of Buffer B

TABLE 4 Concentration of HEPES and of Salts in Buffer B Concentration Component (mM unless otherwise specified) HEPES 25 NaCl 119 KCl 5 CaCl₂ 2 MgCl₂ 2 glucose 6 g/l

In Table 4 the pH adjusted to 7.4 with NaOH

Albumin is an optional component of Buffer B

In some embodiments, drug-loaded platelets are prepared by incubating the platelets with the drug in a loading buffer having the components shown in the table below.

In some embodiments, the loading buffer has the components as listed above in Table 1.

In some embodiments, incubation is performed at 37° C. using a platelet to drug volume ratio of 1:2, using different incubation periods.

Example 1. Permeabilized Platelets

Saponin permeabilizes platelet cell membranes in a concentration dependent manner. Platelets were incubated in the presence of saponin at a concentration of either 5 μg/mL or 7.5 μg/mL to permeabilize platelet cell membranes. 1,4,5-triphosphate (IP3) was added at the time points indicated. Saponin-mediated permeabilization of platelets was measured using standard light transmission aggregometry (LTA) (FIG. 1). Platelets were incubated with increasing concentrations of a detergent (e.g., saponin) and using Hepes modified Tyrode's albumin (HMTA). Cells only bars represent samples in which the platelets were incubated in the absence of Lucifer yellow. Isotype control bars represent samples in which the platelets were incubated in the presence of a reference antibody. Lucifer Yellow bars represent samples in which the platelets were incubated in the presence of Lucifer yellow. FIG. 2 shows the median fluorescence as measured by flow cytometry. The results show a saponin concentration of about 6 μg/ml to about 10 μg/ml resulting in uptake of Lucifer Yellow by the permeabilized platelets.

Example 2. Drug-Loaded Platelets

Platelets were incubated with BODIPY tagged vancomycin in increasing time intervals (0, 2, and 4 hours). The experiment was performed in duplicate with and without the presence of trehalose. FIG. 4 shows flow cytometry data indicating endocytic loading efficiency of the fluorescently-labeled BODIPY-vancomycin via fluid phase endocytosis. These data show that fluorescently-labeled vancomycin was more efficiently loaded into platelets via fluid phase endocytosis at four hours in the presence of trehalose than in the absence of trehalose. FIG. 3 also shows flow cytometry data providing endocytic loading efficiency of other fluorescent conjugates including BODIPY-vancomycin, FITC-bovine IgG, Fab2, and FITC-albumin in platelets.

Example 3. Loading Platelets with Liposome Encapsulated Vancomycin

The starting apheresis platelet material can be pooled and characterized. The platelet pool can be acidified to pH 6.6-6.8 using Acid Citrate Dextrose solution. Platelets can be isolated by centrifugation at ˜1500 g for 20 minutes, with slow acceleration and braking. The supernatant plasma can be aspirated and disposed of.

The platelets can be suspended in Buffer A at a concentration of 200,000 platelets/μl. The components of Buffer A are shown above Table 2.

While the platelets can be centrifuged, liposome-encapsulated vancomycin can be prepared as follows: lyophilized phospholipids (Sigma-Aldrich, SKU#DOX-1000) can be rehydrated with a 2 mg/ml solution of Vancomycin in PBS; the rehydrated mixture can be subjected it to a vortex for 30 seconds and can be incubated at 37° C. for 30 minutes.

The platelets in Tyrode's HEPES buffer and the liposomal Vancomycin can be mixed and the mixture can be incubated at 37° C. for 30 minutes.

The resulting Vancomycin-loaded platelets can be washed in 1 mL Tyrode's HEPES buffer to remove unincorporated liposome by centrifugation at 1500 g for 20 minutes.

Optionally, the lyophilized Vancomycin-loaded platelets can be suspended in water at a concentration suitable for the uses disclosed herein.

Example 4. Hyper/Hypotonic Platelet Loading

Platelets were isolated by centrifugation at 1000 g for 10 minutes. The platelets were then resuspended in a hypertonic pre-treatment solution composed of dextrose at 2.5%, 5%, 10%, and 15% dextrose in PBS at pH 6.5 (w/v). Platelets were then incubated at room temperature for 30 minutes. Following incubation the platelets were again isolated via centrifugation at 1000 g for 10 minutes. The supernatant was aspirated and the platelets were resuspended in loading buffer and incubated at room temperature for 30-60 minutes. Experiments with this method demonstrated significant loading of the fluorescent dye Lucifer yellow for platelets incubated with high osmolarity pre-treatment solutions (FIG. 5). Fluorescence measurements were taken at 0 hours, 0.5 hours, and 1.5 hours. Loading was generally correlated with the osmotic gradient derived from the difference in osmolarity between the pre-treatment solution and the loading solution. 15% dextrose in PBS demonstrated substantially higher loading.

Example 5. Hypertonic/Hypotonic Loaded Platelet Morphology and Viability

Platelet morphology and viability was assessed for each condition with flow cytometry platelet counts (FIG. 6) and flow cytometry measurements of cell size (FIG. 7). Platelets across all conditions maintained relatively stable counts and acceptable cell sizes. Additionally, platelets were tested for functionality at the end of the process (after 1.5 hours of loading) by aggregometry. Platelet aggregation in response to collagen was measured for platelets from each condition. The more hypertonic pre-treatment solutions gave lower aggregation responses, however, the responses were still above the baseline (FIG. 8).

Example 6. Electroporation Loaded Platelets

Phalloidin:

Apheresis platelets were prepared and washed in Loading Buffer (Table 1) to a target concentration of 1,500 k/μl by centrifugation.

Phalloidin-CF488A was added to the prepared platelets to a final concentration of 5 U/mL to the platelet suspension.

Aliquots of the washed platelet suspension and peptide suspension (Phalloidin-CF488A) were electroporated under the following parameters: 2000 V, 0.2 ms, 0.4 cm cuvette width, and exponential waveform. Electroporation was performed with Gene Pulser Xcell Electroporation Systems (Biorad).

The electroporated sample was transferred to a polypropylene microcentrifuge tube and allowed to rest in the dark at room temperature for 30 minutes. The microcentrifuge containing the electroporated sample was inverted by hand every 5 to 10 minutes to prevent sedimentation and to promote mixing. The loaded platelets can be washed and used directly for desired applications. Platelets loaded with Phalloidin-CF® 488A (Biotium, Cat. #00042) were evaluated by flow cytometry for FITC signal post-electroporation.

Variations to this protocol can be made. For example, fresh platelets can also be used and the target concentration of platelets (e.g., fresh platelets, apheresis platelets) can be between about 500,000/μl and about 2,500,000/μl. Also, the electroporation voltage can be varied between 500 V and 3,000 V. The cuvette width may be selected from 0.1 cm, 0.2 cm, or 0.4 cm. Electric pulse waveform may be selected from square waveform or exponential waveform. Pulse duration may be varied between 0.05 ms and 2.0 ms, and the total number of exposures to the electric field may be increased.

FIG. 9 shows that platelets, without electroporation, that are loaded with Phalloidin-CF® 488A (5 U/mL); “Phalloidin no poration”) are indistinguishable from platelets not loaded with Phalloidin-CF® 488A (“Blank”). FIG. 9 also shows that Phalloidin-CF® 488A loading into platelets is not uniform under electroporation conditions at 2000 V, 0.2 ms, exponential waveform in a 0.4 cm cuvette width. Without wishing to be bound by any theory, the non-uniform loading may be the result of the population of cells that may be in different actin polymerization states. Among the electroporated platelets a wide distribution of fluorescence intensity is observed. In total, about 20% of platelets have detectable Phalloidin-CF® 488A.

FIG. 10 shows mean platelet FITC-H intensity by flow cytometry for samples with or without 5 U/mL phalloidin-CF® 488A, and with or without electroporation (2000 V, 0.2 ms, exponential waveform in a 0.4 cm cuvette width). Background fluorescence signal is low for both the sample containing no phalloidin-CF® 488A “Blank” and the sample containing Phalloidin-CF® 488A in the absence of electroporation (“Not Electroporated”). Electroporation in the presence of Phalloidin-CF® 488A (“Electroporated 2 kV 0.2 ms”), the mean FITC-H intensity of the entire platelet population increases more than 10-fold over background.

The results show that Phalloidin-CF® 488A binds filamentous actin and is typically used for high-resolution microscopy. Also, the Phalloidin-CF® 488A accumulates in electroporated cells that also have filamentous actin. The results demonstrate that a peptide which is typically membrane impermeable (e.g. Phalloidin) can be introduced in a selective manner to live platelets.

Streptavidin

Platelets were prepared by the protocol described in this example. The protein used below was Streptavidin-Dylight 488 (ThermoFisher Cat. #21832) at a concentration of 150 μg/mL. Platelets loaded with Streptavidin-Dylight 488 were evaluated by flow cytometry for FITC signal post-electroporation. Streptavidin is typically used for immunostaining and signal amplification in combination with biotin-conjugated antibodies. Streptavidin is not expected to bind specifically to any platelet component.

FIG. 11 is a histogram of platelet+/−Streptavidin-Dylight 488 FITC-H intensity on a biexponential scale. With no electroporation, Platelets loaded with Streptavidin-Dylight 488 (150 μg/mL; “Streptavidin no Poration”) that are not exposed to electroporation have slightly elevated fluorescence background in FITC-H compared to platelets not loaded with Streptavidin-Dylight 488 (“Blank”). Platelets loaded with Streptavidin-Dylight 488 exposed to electroporation (2000 V, 1.0 ms, exponential waveform in a 0.4 cm cuvette width), saw fairly uniform loading, as evidenced by the unimodal platelet population distribution. Among electroporated Streptavidin-Dylight 488 FITC-H loaded platelets over 50% have fluorescence signal over background.

FIG. 12 shows mean platelet FITC-H intensity by flow cytometry for samples with or without 150 μg/mL of Streptavidin-Dylight 488 FITC-H, and with or without electroporation (2000 V, 1.0 ms, exponential waveform in a 0.4 cm cuvette width). Background fluorescence signal is low for the sample containing no Streptavidin-Dylight 488 FITC-H (“Blank”) and is moderately elevated for the sample containing Streptavidin-Dylight 488 FITC-H but absent electroporation (“Not Electroporated”). After electroporation in the presence of Streptavidin-Dylight 488 (“Electroporated 2 kV 1.0 ms”), the mean FITC-H intensity of the entire platelet population increases more than 6 fold over the background.

Lucifer Yellow

Platelets were prepared by the protocol described in this example. The small molecule used was Lucifer Yellow at a concentration of 2.5 mM. Platelets loaded with Lucifer Yellow were evaluated by flow cytometry for AmCyan signal post-electroporation. Lucifer Yellow is a small, membrane impermeable hydrophilic fluorescent molecule that is generally used as a means for measuring endocytosis turnover, and is not expected to bind any platelet-specific components. Platelets were loaded with Lucifer Yellow by electroporation (1400 V, 0.2 ms, 0.4 cm cuvette width, exponential waveform) with one, two, or three exposures to the electric field. Samples were allowed to rest 30 minutes in microcentrifuge tubes between repeated exposures.

FIG. 13 is a histogram showing Lucifer Yellow fluorescence in platelets under various loading conditions. Platelets exposed to one shock at 1400 V had similar Lucifer Yellow loading compared to a platelet sample that endocytosed Lucifer Yellow for three hours in Loading Buffer (Table 1). Maximum Lucifer Yellow fluorophore loading was seen after two shocks at 1400 V, and there was no benefit to additional electroporation cycles after two shocks.

FIG. 14 shows Lucifer Yellow fluorescence in platelets under various loading conditions: no Lucifer Yellow exposure, no electroporation for three hours, one shock, two shocks with a 30 minute rest in between, and three shocks with 30 minute rests between shock 1 and 2 and shock 2 and 3. Maximum Lucifer Yellow fluorophore loading was seen after two shocks at 1400 V.

EXEMPLARY EMBODIMENTS

1. A method of preparing drug-loaded platelets, comprising:

-   -   treating platelets with a drug and with a loading buffer         comprising a salt, a base, a loading agent, and optionally at         least one organic solvent, to form the drug-loaded platelets.

2. A method of preparing drug-loaded platelets, comprising:

-   -   a) providing platelets;         -   and     -   b) treating the platelets with a drug and with a loading buffer         comprising a salt, a base, a loading agent, and optionally at         least one organic solvent to form the drug-loaded platelets.

3. The method of any one of the preceding embodiments, wherein the platelets are treated with the drug and with the buffer sequentially, in either order.

4. A method of preparing drug-loaded platelets, comprising:

-   -   (1) treating platelets with a drug to form a first composition;         and     -   (2) treating the first composition with a buffer comprising a         salt, a base, a loading agent, and optionally at least one         organic solvent, to form the drug-loaded platelets.

5. A method of preparing drug-loaded platelets, comprising:

-   -   (1) treating the platelets with a buffer comprising a salt, a         base, a loading agent, and optionally at least one organic         solvent to form a first composition; and     -   (2) treating the first composition with a drug, to form the         drug-loaded platelets.

6. The method of embodiments 1 or 2, wherein the platelets are treated with the drug and with the buffer concurrently.

7. A method of preparing drug-loaded platelets, comprising:

treating the platelets with a drug in the presence of a buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent to form the drug-loaded platelets.

8. The method of any one of the preceding embodiments, wherein the platelets are pooled from a plurality of donors prior to a treating step.

9. A method of preparing drug-loaded platelets comprising

-   -   A) pooling platelets from a plurality of donors; and     -   B) treating the platelets from step (A) with a drug and with a         loading buffer comprising a salt, a base, a loading agent, and         optionally at least one organic solvent, to form the drug-loaded         platelets.

10. A method of preparing drug-loaded platelets comprising

-   -   A) pooling platelets from a plurality of donors; and     -   B)         -   (1) treating the platelets from step (A) with a drug to form             a first composition; and         -   (2) treating the first composition with a buffer comprising             a salt, a base, a loading agent, and optionally at least one             organic solvent, to form the drug-loaded platelets.

11. A method of preparing drug-loaded platelets comprising

-   -   A) pooling platelets from a plurality of donors; and     -   B)         -   (1) treating the platelets from step (A) with a buffer             comprising a salt, a base, a loading agent, and optionally             at least one organic solvent, to form a first composition;             and         -   (2) treating the first composition with a drug to form the             drug-loaded platelets.

12. A method of preparing drug-loaded platelets comprising

-   -   A) pooling platelets from a plurality of donors; and     -   B) treating the platelets with a drug in the presence of a         buffer comprising a salt, a base, a loading agent, and         optionally at least one organic solvent, to form the drug-loaded         platelets.

13. The method of any one of the preceding embodiments, wherein the loading agent is a monosaccharide or a disaccharide.

14. The method of any one of the preceding embodiments, wherein the loading agent is sucrose, maltose, trehalose, glucose, mannose, or xylose.

15. The method of any one of the preceding embodiments, wherein the platelets are isolated prior to a treating step.

16. The method of any one of the preceding embodiments, wherein the platelets are loaded with the drug in a period of time of 5 minutes to 48 hours.

17. The method of any one of the preceding embodiments, wherein the concentration of drug in the drug-loaded platelets is from about 1 nM to about 100 mM.

18. The method of any one of the preceding embodiments, wherein the one or more organic solvents selected from the group consisting of ethanol, acetic acid, acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, dioxane, methanol, n-propanol, isopropanol, tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide (DMAC), or combinations thereof.

19. The method of any one of the preceding embodiments, further comprising cold storing, cryopreserving, freeze-drying, thawing, rehydrating, and combinations thereof the drug-loaded platelets.

20. The method of embodiment 19, wherein the drying step comprises freeze-drying the drug-loaded platelets.

21. The method of embodiment 19 or 20, further comprising rehydrating the drug-loaded platelets obtained from the drying step.

22. Drug-loaded platelets prepared by the method of any one of the preceding embodiments.

23. Rehydrated drug-loaded platelets prepared by a method comprising rehydrating the drug-loaded platelets of embodiment 22.

24. The method of any one of the preceding embodiments, wherein the drug is modified with an imaging agent.

25. The method of embodiment 24, wherein the drug is modified with the imaging agent prior to treating platelets with the drug.

26. The method of any one of the preceding embodiments, wherein the platelets are further treated with an imaging agent, wherein the drug-loaded platelets are loaded with the imaging agent.

27. The method of any one of the preceding embodiments, wherein the method does not comprise treating the platelets with an organic solvent.

28. The method of any one of embodiments 4, 5, 10 or 11, wherein the method does not comprise treating the first composition with an organic solvent.

29. The method of any one of the preceding embodiments, wherein the method comprises treating the platelets with Prostaglandin E1 (PGE1) or Prostacyclin.

30. The method of any one of embodiments 1 to 28, wherein the method does not comprise treating the platelets with Prostaglandin E1 (PGE1) or Prostacyclin.

31. The method of any one of the preceding embodiments, wherein the method comprises treating the platelets with a chelating agent such as EGTA.

32. The method of any one of embodiments 1 to 30, wherein the method does not comprises treating the platelets with a chelating agent such as EGTA.

33. The method of any one of embodiments 1 to 29, wherein the method comprises treating the first composition with Prostaglandin E1 (PGE1) or Prostacyclin.

34. The method of any one of embodiments 1 to 28 or 30, wherein the method does not comprise treating the first composition with Prostaglandin E1 (PGE1) or Prostacyclin.

35. The method of any one of embodiments 1 to 31, 33 or 34, wherein the method comprises treating the first composition with a chelating agent such as EGTA.

36. The method of any one of embodiments 1 to 30 or 32 to 34, wherein the method does not comprise treating the first composition with a chelating agent such as EGTA.

37. The method of any one of the preceding claims, wherein the drug is a small molecule, a protein, an oligopeptide, an aptamer, or combinations thereof. 

1. A method of preparing drug-loaded platelets, comprising: treating platelets with a drug and with a loading buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent, to form the drug-loaded platelets.
 2. (canceled)
 3. The method of claim 1, wherein the platelets are treated with the drug and with the buffer sequentially, in either order.
 4. (canceled)
 5. (canceled)
 6. The method of claim 1, wherein the platelets are treated with the drug and with the buffer concurrently.
 7. A method of preparing drug-loaded platelets, comprising: treating the platelets with a drug in the presence of a buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent to form the drug-loaded platelets.
 8. The method of claim 1, wherein the platelets are pooled from a plurality of donors prior to a treating step.
 9. A method of preparing drug-loaded platelets comprising A) pooling platelets from a plurality of donors; and B) treating the platelets from step (A) with a drug and with a loading buffer comprising a salt, a base, a loading agent, and optionally at least one organic solvent, to form the drug-loaded platelets.
 10. (canceled)
 11. (canceled)
 12. (canceled)
 13. The method of claim 1, wherein the loading agent is a monosaccharide or a disaccharide.
 14. The method of claim 1, wherein the loading agent is sucrose, maltose, trehalose, glucose, mannose, or xylose.
 15. (canceled)
 16. The method of claim 1, wherein the platelets are loaded with the drug in a period of time of 5 minutes to 48 hours.
 17. The method of claim 1, wherein the concentration of drug in the drug-loaded platelets is from about 1 nM to about 100 mM.
 18. The method of claim 1, wherein the one or more organic solvents selected from the group consisting of ethanol, acetic acid, acetone, acetonitrile, dimethylformamide, dimethyl sulfoxide, dioxane, methanol, n-propanol, isopropanol, tetrahydrofuran (THF), N-methyl pyrrolidone, dimethylacetamide (DMAC), or combinations thereof.
 19. The method of claim 1, further comprising cold storing, cryopreserving, freeze-drying, thawing, or rehydrating, or combinations thereof, the drug-loaded platelets.
 20. (canceled)
 21. The method of claim 19, rehydrating the drug-loaded platelets obtained from the freeze-drying step.
 22. Drug-loaded platelets prepared by the method of claim
 1. 23. Rehydrated drug-loaded platelets prepared by a method comprising rehydrating the drug-loaded platelets of claim
 22. 24. The method of claim 1, wherein the drug is modified with an imaging agent.
 25. The method of claim 24, wherein the drug is modified with the imaging agent prior to treating platelets with the drug.
 26. (canceled)
 27. (canceled)
 28. (canceled)
 29. The method of claim 1, wherein the method comprises treating the platelets with Prostaglandin E1 (PGE1) or Prostacyclin.
 30. (canceled)
 31. The method of claim 1, wherein the method comprises treating the platelets with a chelating agent such as EGTA.
 32. (canceled)
 33. (canceled)
 34. (canceled)
 35. (canceled)
 36. (canceled)
 37. The method of claim 1, wherein the drug is a small molecule, a protein, an oligopeptide, an aptamer, or combinations thereof.
 38. The method of claim 1, wherein the loading buffer comprises at least one organic solvent. 